diff --git src/bp-activity/bp-activity-notifications.php src/bp-activity/bp-activity-notifications.php
index a5ce0ed..e4fee0f 100644
--- src/bp-activity/bp-activity-notifications.php
+++ src/bp-activity/bp-activity-notifications.php
@@ -180,27 +180,29 @@ To view and respond to the message, log in and visit: %3$s
 function bp_activity_new_comment_notification( $comment_id = 0, $commenter_id = 0, $params = array() ) {
 
 	// Set some default parameters
-	$activity_id = 0;
-	$parent_id   = 0;
-
-	extract( $params );
-
-	$original_activity = new BP_Activity_Activity( $activity_id );
-
-	if ( $original_activity->user_id != $commenter_id && 'no' != bp_get_user_meta( $original_activity->user_id, 'notification_activity_new_reply', true ) ) {
-		$poster_name   = bp_core_get_user_displayname( $commenter_id );
-		$thread_link   = bp_activity_get_permalink( $activity_id );
-		$settings_slug = function_exists( 'bp_get_settings_slug' ) ? bp_get_settings_slug() : 'settings';
-		$settings_link = bp_core_get_user_domain( $original_activity->user_id ) . $settings_slug . '/notifications/';
-
-		$poster_name = stripslashes( $poster_name );
-		$content = bp_activity_filter_kses( stripslashes($content) );
-
-		// Set up and send the message
-		$ud      = bp_core_get_core_userdata( $original_activity->user_id );
-		$to      = $ud->user_email;
-		$subject = bp_get_email_subject( array( 'text' => sprintf( __( '%s replied to one of your updates', 'buddypress' ), $poster_name ) ) );
-		$message = sprintf( __(
+	$reply = (object) wp_parse_args( $params, array(
+		'activity_id' => 0,
+		'parent_id'   => 0,
+	) );
+
+	$original_activity = new BP_Activity_Activity( $reply->activity_id );
+
+	if ( $original_activity->user_id != $commenter_id ) {
+		// Send an email if the user has not disabled it
+		if ( 'no' != bp_get_user_meta( $original_activity->user_id, 'notification_activity_new_reply', true ) ) {
+			$poster_name   = bp_core_get_user_displayname( $commenter_id );
+			$thread_link   = bp_activity_get_permalink( $reply->activity_id );
+			$settings_slug = function_exists( 'bp_get_settings_slug' ) ? bp_get_settings_slug() : 'settings';
+			$settings_link = bp_core_get_user_domain( $original_activity->user_id ) . $settings_slug . '/notifications/';
+
+			$poster_name = stripslashes( $poster_name );
+			$content = bp_activity_filter_kses( stripslashes( $reply->content ) );
+
+			// Set up and send the message
+			$ud      = bp_core_get_core_userdata( $original_activity->user_id );
+			$to      = $ud->user_email;
+			$subject = bp_get_email_subject( array( 'text' => sprintf( __( '%s replied to one of your updates', 'buddypress' ), $poster_name ) ) );
+			$message = sprintf( __(
 '%1$s replied to one of your updates:
 
 "%2$s"
@@ -210,83 +212,98 @@ To view your original update and all comments, log in and visit: %3$s
 ---------------------
 ', 'buddypress' ), $poster_name, $content, $thread_link );
 
-		// Only show the disable notifications line if the settings component is enabled
-		if ( bp_is_active( 'settings' ) ) {
-			$message .= sprintf( __( 'To disable these notifications please log in and go to: %s', 'buddypress' ), $settings_link );
-		}
-
-		/**
-		 * Filters the user email that the new comment notification will be sent to.
-		 *
-		 * @since BuddyPress (1.2.0)
-		 *
-		 * @param string $to User email the notification is being sent to.
-		 */
-		$to = apply_filters( 'bp_activity_new_comment_notification_to', $to );
+			// Only show the disable notifications line if the settings component is enabled
+			if ( bp_is_active( 'settings' ) ) {
+				$message .= sprintf( __( 'To disable these notifications please log in and go to: %s', 'buddypress' ), $settings_link );
+			}
 
-		/**
-		 * Filters the new comment notification subject that will be sent to user.
-		 *
-		 * @since BuddyPress (1.2.0)
-		 *
-		 * @param string $subject Email notification subject text.
-		 * @param string $poster_name Name of the person who made the comment.
-		 */
-		$subject = apply_filters( 'bp_activity_new_comment_notification_subject', $subject, $poster_name );
+			/**
+			 * Filters the user email that the new comment notification will be sent to.
+			 *
+			 * @since BuddyPress (1.2.0)
+			 *
+			 * @param string $to User email the notification is being sent to.
+			 */
+			$to = apply_filters( 'bp_activity_new_comment_notification_to', $to );
+
+			/**
+			 * Filters the new comment notification subject that will be sent to user.
+			 *
+			 * @since BuddyPress (1.2.0)
+			 *
+			 * @param string $subject Email notification subject text.
+			 * @param string $poster_name Name of the person who made the comment.
+			 */
+			$subject = apply_filters( 'bp_activity_new_comment_notification_subject', $subject, $poster_name );
+
+			/**
+			 * Filters the new comment notification message that will be sent to user.
+			 *
+			 * @since BuddyPress (1.2.0)
+			 *
+			 * @param string $message Email notification message text.
+			 * @param string $poster_name Name of the person who made the comment.
+			 * @param string $content Content of the comment.
+			 * @param string $thread_link URL permalink for the activity thread.
+			 * @param string $settings_link URL permalink for the user's notification settings area.
+			 */
+			$message = apply_filters( 'bp_activity_new_comment_notification_message', $message, $poster_name, $content, $thread_link, $settings_link );
+
+			wp_mail( $to, $subject, $message );
+
+			/**
+			 * Fires after the sending of a reply to an update email notification.
+			 *
+			 * @since BuddyPress (1.5.0)
+			 *
+			 * @param int    $user_id ID of the original activity item author.
+			 * @param string $subject Email notification subject text.
+			 * @param string $message Email notification message text.
+			 * @param int    $comment_id ID for the newly received comment.
+			 * @param int    $commenter_id ID of the user who made the comment.
+			 * @param array  $params Arguments used with the original activity comment.
+			 */
+			do_action( 'bp_activity_sent_reply_to_update_email', $original_activity->user_id, $subject, $message, $comment_id, $commenter_id, $params );
+		}
 
 		/**
-		 * Filters the new comment notification message that will be sent to user.
+		 * Triggers the update_reply notification.
 		 *
-		 * @since BuddyPress (1.2.0)
+		 * @since BuddyPress (?)
 		 *
-		 * @param string $message Email notification message text.
-		 * @param string $poster_name Name of the person who made the comment.
-		 * @param string $content Content of the comment.
-		 * @param string $thread_link URL permalink for the activity thread.
-		 * @param string $settings_link URL permalink for the user's notification settings area.
+		 * @param BP_Activity_Activity $original_activity the original activity.
+		 * @param int                  $comment_id ID for the newly received comment.
+		 * @param int                  $commenter_id ID of the user who made the comment.
+		 * @param object               $reply Arguments used with the original activity comment.
 		 */
-		$message = apply_filters( 'bp_activity_new_comment_notification_message', $message, $poster_name, $content, $thread_link, $settings_link );
-
-		wp_mail( $to, $subject, $message );
-
-		/**
-		 * Fires after the sending of a reply to an update email notification.
-		 *
-		 * @since BuddyPress (1.5.0)
-		 *
-		 * @param int    $user_id ID of the original activity item author.
-		 * @param string $subject Email notification subject text.
-		 * @param string $message Email notification message text.
-		 * @param int    $comment_id ID for the newly received comment.
-		 * @param int    $commenter_id ID of the user who made the comment.
-		 * @param array  $params Arguments used with the original activity comment.
-		 */
-		do_action( 'bp_activity_sent_reply_to_update_email', $original_activity->user_id, $subject, $message, $comment_id, $commenter_id, $params );
+		do_action( 'bp_activity_sent_reply_to_update_notification', $original_activity, $comment_id, $commenter_id, $reply );
 	}
 
 	/***
 	 * If this is a reply to another comment, send an email notification to the
 	 * author of the immediate parent comment.
 	 */
-	if ( empty( $parent_id ) || ( $activity_id == $parent_id ) ) {
+	if ( empty( $reply->parent_id ) || ( $reply->activity_id == $reply->parent_id ) ) {
 		return false;
 	}
 
-	$parent_comment = new BP_Activity_Activity( $parent_id );
+	$parent_comment = new BP_Activity_Activity( $reply->parent_id );
 
-	if ( $parent_comment->user_id != $commenter_id && $original_activity->user_id != $parent_comment->user_id && 'no' != bp_get_user_meta( $parent_comment->user_id, 'notification_activity_new_reply', true ) ) {
-		$poster_name   = bp_core_get_user_displayname( $commenter_id );
-		$thread_link   = bp_activity_get_permalink( $activity_id );
-		$settings_slug = function_exists( 'bp_get_settings_slug' ) ? bp_get_settings_slug() : 'settings';
-		$settings_link = bp_core_get_user_domain( $parent_comment->user_id ) . $settings_slug . '/notifications/';
+	if ( $parent_comment->user_id != $commenter_id && $original_activity->user_id != $parent_comment->user_id ) {
+		// Send an email if the user has not disabled it
+		if ( 'no' != bp_get_user_meta( $parent_comment->user_id, 'notification_activity_new_reply', true ) ) {
+			$poster_name   = bp_core_get_user_displayname( $commenter_id );
+			$thread_link   = bp_activity_get_permalink( $reply->activity_id );
+			$settings_slug = function_exists( 'bp_get_settings_slug' ) ? bp_get_settings_slug() : 'settings';
+			$settings_link = bp_core_get_user_domain( $parent_comment->user_id ) . $settings_slug . '/notifications/';
 
-		// Set up and send the message
-		$ud       = bp_core_get_core_userdata( $parent_comment->user_id );
-		$to       = $ud->user_email;
-		$subject = bp_get_email_subject( array( 'text' => sprintf( __( '%s replied to one of your comments', 'buddypress' ), $poster_name ) ) );
+			// Set up and send the message
+			$ud       = bp_core_get_core_userdata( $parent_comment->user_id );
+			$to       = $ud->user_email;
+			$subject = bp_get_email_subject( array( 'text' => sprintf( __( '%s replied to one of your comments', 'buddypress' ), $poster_name ) ) );
 
-		$poster_name = stripslashes( $poster_name );
-		$content = bp_activity_filter_kses( stripslashes( $content ) );
+			$poster_name = stripslashes( $poster_name );
+			$content = bp_activity_filter_kses( stripslashes( $reply->content ) );
 
 $message = sprintf( __(
 '%1$s replied to one of your comments:
@@ -298,58 +315,71 @@ To view the original activity, your comment and all replies, log in and visit: %
 ---------------------
 ', 'buddypress' ), $poster_name, $content, $thread_link );
 
-		// Only show the disable notifications line if the settings component is enabled
-		if ( bp_is_active( 'settings' ) ) {
-			$message .= sprintf( __( 'To disable these notifications please log in and go to: %s', 'buddypress' ), $settings_link );
-		}
-
-		/**
-		 * Filters the user email that the new comment reply notification will be sent to.
-		 *
-		 * @since BuddyPress (1.2.0)
-		 *
-		 * @param string $to User email the notification is being sent to.
-		 */
-		$to = apply_filters( 'bp_activity_new_comment_notification_comment_author_to', $to );
-
-		/**
-		 * Filters the new comment reply notification subject that will be sent to user.
-		 *
-		 * @since BuddyPress (1.2.0)
-		 *
-		 * @param string $subject Email notification subject text.
-		 * @param string $poster_name Name of the person who made the comment reply.
-		 */
-		$subject = apply_filters( 'bp_activity_new_comment_notification_comment_author_subject', $subject, $poster_name );
-
-		/**
-		 * Filters the new comment reply notification message that will be sent to user.
-		 *
-		 * @since BuddyPress (1.2.0)
-		 *
-		 * @param string $message Email notification message text.
-		 * @param string $poster_name Name of the person who made the comment reply.
-		 * @param string $content Content of the comment reply.
-		 * @param string $settings_link URL permalink for the user's notification settings area.
-		 * @param string $thread_link URL permalink for the activity thread.
-		 */
-		$message = apply_filters( 'bp_activity_new_comment_notification_comment_author_message', $message, $poster_name, $content, $settings_link, $thread_link );
+			// Only show the disable notifications line if the settings component is enabled
+			if ( bp_is_active( 'settings' ) ) {
+				$message .= sprintf( __( 'To disable these notifications please log in and go to: %s', 'buddypress' ), $settings_link );
+			}
 
-		wp_mail( $to, $subject, $message );
+			/**
+			 * Filters the user email that the new comment reply notification will be sent to.
+			 *
+			 * @since BuddyPress (1.2.0)
+			 *
+			 * @param string $to User email the notification is being sent to.
+			 */
+			$to = apply_filters( 'bp_activity_new_comment_notification_comment_author_to', $to );
+
+			/**
+			 * Filters the new comment reply notification subject that will be sent to user.
+			 *
+			 * @since BuddyPress (1.2.0)
+			 *
+			 * @param string $subject Email notification subject text.
+			 * @param string $poster_name Name of the person who made the comment reply.
+			 */
+			$subject = apply_filters( 'bp_activity_new_comment_notification_comment_author_subject', $subject, $poster_name );
+
+			/**
+			 * Filters the new comment reply notification message that will be sent to user.
+			 *
+			 * @since BuddyPress (1.2.0)
+			 *
+			 * @param string $message Email notification message text.
+			 * @param string $poster_name Name of the person who made the comment reply.
+			 * @param string $content Content of the comment reply.
+			 * @param string $settings_link URL permalink for the user's notification settings area.
+			 * @param string $thread_link URL permalink for the activity thread.
+			 */
+			$message = apply_filters( 'bp_activity_new_comment_notification_comment_author_message', $message, $poster_name, $content, $settings_link, $thread_link );
+
+			wp_mail( $to, $subject, $message );
+
+			/**
+			 * Fires after the sending of a reply to a reply email notification.
+			 *
+			 * @since BuddyPress (1.5.0)
+			 *
+			 * @param int    $user_id ID of the parent activity item author.
+			 * @param string $subject Email notification subject text.
+			 * @param string $message Email notification message text.
+			 * @param int    $comment_id ID for the newly received comment.
+			 * @param int    $commenter_id ID of the user who made the comment.
+			 * @param array  $params Arguments used with the original activity comment.
+			 */
+			do_action( 'bp_activity_sent_reply_to_reply_email', $parent_comment->user_id, $subject, $message, $comment_id, $commenter_id, $params );
+		}
 
 		/**
-		 * Fires after the sending of a reply to a reply email notification.
+		 * Triggers the comment_reply notification.
 		 *
-		 * @since BuddyPress (1.5.0)
+		 * @since BuddyPress (?)
 		 *
-		 * @param int    $user_id ID of the parent activity item author.
-		 * @param string $subject Email notification subject text.
-		 * @param string $message Email notification message text.
-		 * @param int    $comment_id ID for the newly received comment.
-		 * @param int    $commenter_id ID of the user who made the comment.
-		 * @param array  $params Arguments used with the original activity comment.
+		 * @param BP_Activity_Activity $parent_comment the parent activity.
+		 * @param int                  $comment_id ID for the newly received comment.
+		 * @param int                  $commenter_id ID of the user who made the comment.
+		 * @param object               $reply Arguments used with the original activity comment.
 		 */
-		do_action( 'bp_activity_sent_reply_to_reply_email', $parent_comment->user_id, $subject, $message, $comment_id, $commenter_id, $params );
+		do_action( 'bp_activity_sent_reply_to_reply_notification', $parent_comment, $comment_id, $commenter_id, $reply );
 	}
 }
 
@@ -387,6 +417,8 @@ add_action( 'bp_activity_comment_posted', 'bp_activity_new_comment_notification_
  * @return string $return Formatted @mention notification.
  */
 function bp_activity_format_notifications( $action, $item_id, $secondary_item_id, $total_items, $format = 'string' ) {
+	// Initilialize the returned value
+	$return = false;
 
 	switch ( $action ) {
 		case 'new_at_mention':
@@ -403,48 +435,163 @@ function bp_activity_format_notifications( $action, $item_id, $secondary_item_id
 				$user_fullname = bp_core_get_user_displayname( $poster_user_id );
 				$text =  sprintf( __( '%1$s mentioned you', 'buddypress' ), $user_fullname );
 			}
+
+			if ( 'string' == $format ) {
+				/**
+				 * Filters the @mention notification for the string format.
+				 *
+				 * This is a variable filter that is dependent on how many items
+				 * need notified about. The two possible hooks are bp_activity_single_at_mentions_notification
+				 * or bp_activity_multiple_at_mentions_notification.
+				 *
+				 * @since BuddyPress (1.5.0)
+				 *
+				 * @param string $string HTML anchor tag for the mention.
+				 * @param string $at_mention_link The permalink for the mention.
+				 * @param int    $total_items How many items being notified about.
+				 * @param int    $activity_id ID of the activity item being formatted.
+				 * @param int    $poster_user_id ID of the user posting the mention.
+				 */
+				$return = apply_filters( 'bp_activity_' . $amount . '_at_mentions_notification', '<a href="' . esc_url( $at_mention_link ) . '" title="' . esc_attr( $at_mention_title ) . '">' . esc_html( $text ) . '</a>', $at_mention_link, (int) $total_items, $activity_id, $poster_user_id );
+			} else {
+
+				/**
+				 * Filters the @mention notification for any non-string format.
+				 *
+				 * This is a variable filter that is dependent on how many items need notified about.
+				 * The two possible hooks are bp_activity_single_at_mentions_notification
+				 * or bp_activity_multiple_at_mentions_notification.
+				 *
+				 * @since BuddyPress (1.5.0)
+				 *
+				 * @param array  $array Array holding the content and permalink for the mention notification.
+				 * @param string $at_mention_link The permalink for the mention.
+				 * @param int    $total_items How many items being notified about.
+				 * @param int    $activity_id ID of the activity item being formatted.
+				 * @param int    $poster_user_id ID of the user posting the mention.
+				 */
+				$return = apply_filters( 'bp_activity_' . $amount . '_at_mentions_notification', array(
+					'text' => $text,
+					'link' => $at_mention_link
+				), $at_mention_link, (int) $total_items, $activity_id, $poster_user_id );
+			}
 		break;
-	}
 
-	if ( 'string' == $format ) {
+		case 'update_reply':
+			$activity_id  = $item_id;
+			$commenter_id = $secondary_item_id;
+			$reply_link   = bp_get_notifications_permalink();
+			$reply_title  = __( 'New Activity reply', 'buddypress' );
+			$amount       = 'single';
 
-		/**
-		 * Filters the @mention notification for the string format.
-		 *
-		 * This is a variable filter that is dependent on how many items
-		 * need notified about. The two possible hooks are bp_activity_single_at_mentions_notification
-		 * or bp_activity_multiple_at_mentions_notification.
-		 *
-		 * @since BuddyPress (1.5.0)
-		 *
-		 * @param string $string HTML anchor tag for the mention.
-		 * @param string $at_mention_link The permalink for the mention.
-		 * @param int    $total_items How many items being notified about.
-		 * @param int    $activity_id ID of the activity item being formatted.
-		 * @param int    $poster_user_id ID of the user posting the mention.
-		 */
-		$return = apply_filters( 'bp_activity_' . $amount . '_at_mentions_notification', '<a href="' . esc_url( $at_mention_link ) . '" title="' . esc_attr( $at_mention_title ) . '">' . esc_html( $text ) . '</a>', $at_mention_link, (int) $total_items, $activity_id, $poster_user_id );
-	} else {
+			if ( (int) $total_items > 1 ) {
+				$reply_link = add_query_arg( 'type', $action, $reply_link );
+				$text = sprintf( __( 'You have %1$d new replies', 'buddypress' ), (int) $total_items );
+				$amount = 'multiple';
+			} else {
+				$reply_link    = bp_activity_get_permalink( $activity_id );
+				$user_fullname = bp_core_get_user_displayname( $commenter_id );
+				$text =  sprintf( __( '%1$s commented one your updates', 'buddypress' ), $user_fullname );
+			}
 
-		/**
-		 * Filters the @mention notification for any non-string format.
-		 *
-		 * This is a variable filter that is dependent on how many items need notified about.
-		 * The two possible hooks are bp_activity_single_at_mentions_notification
-		 * or bp_activity_multiple_at_mentions_notification.
-		 *
-		 * @since BuddyPress (1.5.0)
-		 *
-		 * @param array  $array Array holding the content and permalink for the mention notification.
-		 * @param string $at_mention_link The permalink for the mention.
-		 * @param int    $total_items How many items being notified about.
-		 * @param int    $activity_id ID of the activity item being formatted.
-		 * @param int    $poster_user_id ID of the user posting the mention.
-		 */
-		$return = apply_filters( 'bp_activity_' . $amount . '_at_mentions_notification', array(
-			'text' => $text,
-			'link' => $at_mention_link
-		), $at_mention_link, (int) $total_items, $activity_id, $poster_user_id );
+			if ( 'string' == $format ) {
+				/**
+				 * Filters the update_reply notification for the string format.
+				 *
+				 * This is a variable filter that is dependent on how many items
+				 * need notified about. The two possible hooks are bp_activity_single_update_reply_notification
+				 * or bp_activity_multiple_update_reply_notification.
+				 *
+				 * @since BuddyPress (?)
+				 *
+				 * @param string $string HTML anchor tag for the update_reply.
+				 * @param string $reply_link The permalink for the activity notification.
+				 * @param int    $total_items How many items being notified about.
+				 * @param int    $activity_id ID of the activity item being formatted.
+				 * @param int    $commenter_id ID of the user posting the reply.
+				 */
+				$return = apply_filters( 'bp_activity_' . $amount . '_update_reply_notification', '<a href="' . esc_url( $reply_link ) . '" title="' . esc_attr( $reply_title ) . '">' . esc_html( $text ) . '</a>', $reply_link, (int) $total_items, $activity_id, $commenter_id );
+			} else {
+
+				/**
+				 * Filters the update_reply notification for any non-string format.
+				 *
+				 * This is a variable filter that is dependent on how many items need notified about.
+				 * The two possible hooks are bp_activity_single_update_reply_notification
+				 * or bp_activity_multiple_update_reply_notification.
+				 *
+				 * @since BuddyPress (?)
+				 *
+				 * @param array  $array Array holding the content and permalink for the update_reply notification.
+				 * @param string $reply_link The permalink for the mention.
+				 * @param int    $total_items How many items being notified about.
+				 * @param int    $activity_id ID of the activity item being formatted.
+				 * @param int    $commenter_id ID of the user posting the reply.
+				 */
+				$return = apply_filters( 'bp_activity_' . $amount . '_update_reply_notification', array(
+					'text' => $text,
+					'link' => $reply_link
+				), $reply_link, (int) $total_items, $activity_id, $commenter_id );
+			}
+		break;
+
+		case 'comment_reply':
+			$activity_id  = $item_id;
+			$commenter_id = $secondary_item_id;
+			$reply_link   = bp_get_notifications_permalink();
+			$reply_title  = __( 'New Activity comment reply', 'buddypress' );
+			$amount       = 'single';
+
+			if ( (int) $total_items > 1 ) {
+				$reply_link = add_query_arg( 'type', $action, $reply_link );
+				$text = sprintf( __( 'You have %1$d new comment replies', 'buddypress' ), (int) $total_items );
+				$amount = 'multiple';
+			} else {
+				$reply_link    = bp_activity_get_permalink( $activity_id );
+				$user_fullname = bp_core_get_user_displayname( $commenter_id );
+				$text =  sprintf( __( '%1$s replied to one your activity comments', 'buddypress' ), $user_fullname );
+			}
+
+			if ( 'string' == $format ) {
+				/**
+				 * Filters the comment_reply notification for the string format.
+				 *
+				 * This is a variable filter that is dependent on how many items
+				 * need notified about. The two possible hooks are bp_activity_single_update_reply_notification
+				 * or bp_activity_multiple_comment_reply_notification.
+				 *
+				 * @since BuddyPress (?)
+				 *
+				 * @param string $string HTML anchor tag for the comment_reply.
+				 * @param string $reply_link The permalink for the activity notification.
+				 * @param int    $total_items How many items being notified about.
+				 * @param int    $activity_id ID of the activity item being formatted.
+				 * @param int    $commenter_id ID of the user posting the reply.
+				 */
+				$return = apply_filters( 'bp_activity_' . $amount . '_comment_reply_notification', '<a href="' . esc_url( $reply_link ) . '" title="' . esc_attr( $reply_title ) . '">' . esc_html( $text ) . '</a>', $reply_link, (int) $total_items, $activity_id, $commenter_id );
+			} else {
+
+				/**
+				 * Filters the comment_reply notification for any non-string format.
+				 *
+				 * This is a variable filter that is dependent on how many items need notified about.
+				 * The two possible hooks are bp_activity_single_comment_reply_notification
+				 * or bp_activity_multiple_comment_reply_notification.
+				 *
+				 * @since BuddyPress (?)
+				 *
+				 * @param array  $array Array holding the content and permalink for the comment_reply notification.
+				 * @param string $reply_link The permalink for the activity notification.
+				 * @param int    $total_items How many items being notified about.
+				 * @param int    $activity_id ID of the activity item being formatted.
+				 * @param int    $commenter_id ID of the user posting the reply.
+				 */
+				$return = apply_filters( 'bp_activity_' . $amount . '_comment_reply_notification', array(
+					'text' => $text,
+					'link' => $reply_link
+				), $reply_link, (int) $total_items, $activity_id, $commenter_id );
+			}
+		break;
 	}
 
 	/**
@@ -454,7 +601,7 @@ function bp_activity_format_notifications( $action, $item_id, $secondary_item_id
 	 *
 	 * @param string $action The type of activity item.
 	 * @param int    $item_id The activity ID.
-	 * @param int    $secondary_item_id @mention mentioner ID.
+	 * @param int    $secondary_item_id the user ID who inited the interaction.
 	 * @param int    $total_items Total amount of items to format.
 	 */
 	do_action( 'activity_format_notifications', $action, $item_id, $secondary_item_id, $total_items );
@@ -494,6 +641,60 @@ function bp_activity_at_mention_add_notification( $activity, $subject, $message,
 add_action( 'bp_activity_sent_mention_email', 'bp_activity_at_mention_add_notification', 10, 5 );
 
 /**
+ * Notify a member one of their activity received a reply.
+ *
+ * Hooked to the 'bp_activity_sent_reply_to_update_notification' action
+ *
+ * @since BuddyPress (?)
+ *
+ * @param BP_Activity_Activity $activity the original activity.
+ * @param int                  $comment_id ID for the newly received comment.
+ * @param int                  $commenter_id ID of the user who made the comment.
+ * @param object               $reply Arguments used with the original activity comment.
+ */
+function bp_activity_update_reply_add_notification( $activity, $comment_id, $commenter_id ) {
+	if ( bp_is_active( 'notifications' ) ) {
+		bp_notifications_add_notification( array(
+			'user_id'           => $activity->user_id,
+			'item_id'           => $activity->id,
+			'secondary_item_id' => $commenter_id,
+			'component_name'    => buddypress()->activity->id,
+			'component_action'  => 'update_reply',
+			'date_notified'     => bp_core_current_time(),
+			'is_new'            => 1,
+		) );
+	}
+}
+add_action( 'bp_activity_sent_reply_to_update_notification', 'bp_activity_update_reply_add_notification', 10, 3 );
+
+/**
+ * Notify a member one of their activity comment received a reply.
+ *
+ * Hooked to the 'bp_activity_sent_reply_to_update_notification' action
+ *
+ * @since BuddyPress (?)
+ *
+ * @param BP_Activity_Activity $activity_comment the parent activity.
+ * @param int                  $comment_id ID for the newly received comment.
+ * @param int                  $commenter_id ID of the user who made the comment.
+ * @param object               $reply Arguments used with the original activity comment.
+ */
+function bp_activity_comment_reply_add_notification( $activity_comment, $comment_id, $commenter_id ) {
+	if ( bp_is_active( 'notifications' ) ) {
+		bp_notifications_add_notification( array(
+			'user_id'           => $activity_comment->user_id,
+			'item_id'           => $activity_comment->item_id,
+			'secondary_item_id' => $commenter_id,
+			'component_name'    => buddypress()->activity->id,
+			'component_action'  => 'comment_reply',
+			'date_notified'     => bp_core_current_time(),
+			'is_new'            => 1,
+		) );
+	}
+}
+add_action( 'bp_activity_sent_reply_to_reply_notification', 'bp_activity_comment_reply_add_notification', 10, 3 );
+
+/**
  * Mark at-mention notifications as read when users visit their Mentions page.
  *
  * @since BuddyPress (1.5.0)
@@ -531,10 +732,30 @@ function bp_activity_remove_screen_notifications_single_activity_permalink( $act
 	// Mark as read any notifications for the current user related to this
 	// activity item
 	bp_notifications_mark_notifications_by_item_id( bp_loggedin_user_id(), $activity->id, buddypress()->activity->id, 'new_at_mention' );
+	bp_notifications_mark_notifications_by_item_id( bp_loggedin_user_id(), $activity->id, buddypress()->activity->id, 'update_reply' );
+	bp_notifications_mark_notifications_by_item_id( bp_loggedin_user_id(), $activity->id, buddypress()->activity->id, 'comment_reply' );
 }
 add_action( 'bp_activity_screen_single_activity_permalink', 'bp_activity_remove_screen_notifications_single_activity_permalink' );
 
 /**
+ * Mark activity notification as read when user visits their notifications unread screen.
+ *
+ * @since BuddyPress (?)
+ */
+function bp_activity_remove_multiple_notifications() {
+	if ( ! bp_is_active( 'notifications' ) || ! isset( $_GET['type'] ) ) {
+		return;
+	}
+
+	if ( ! bp_is_my_profile() ) {
+		return;
+	}
+
+	bp_notifications_mark_notifications_by_type( bp_loggedin_user_id(), buddypress()->activity->id, sanitize_key( $_GET['type'] ) );
+}
+add_action( 'notifications_loop_end', 'bp_activity_remove_multiple_notifications' );
+
+/**
  * Delete at-mention notifications when the corresponding activity item is deleted.
  *
  * @since BuddyPress (2.0.0)
