bp_activity_remove_screen_notifications_single_post()

function bp_activity_remove_screen_notifications_single_post() {

	$reply_id         = filter_input( INPUT_GET, 'rid', FILTER_VALIDATE_INT );
	$comment_reply_id = filter_input( INPUT_GET, 'crid', FILTER_VALIDATE_INT );

	if (
		! is_single()
		|| (
			empty( $reply_id )
			&& empty( $comment_reply_id )
		)
	) {
		return;
	}

	$comment_id = 0;
	// For replies to a parent update.
	if ( ! empty( $reply_id ) ) {
		$comment_id = $reply_id;

		// For replies to an activity comment.
	} elseif ( ! empty( $comment_reply_id ) ) {
		$comment_id = (int) $comment_reply_id;
	}

	// Mark individual activity reply notification as read.
	if ( ! empty( $comment_id ) ) {
		BP_Notifications_Notification::update(
			array(
				'is_new' => false,
			),
			array(
				'user_id' => bp_loggedin_user_id(),
				'id'      => $comment_id,
			)
		);
	}
}