function bp_activity_format_activity_action_custom_post_type_comment( $action, $activity ) {
	$bp = buddypress();

	// Fetch all the tracked post types once.
	if ( empty( $bp->activity->track ) ) {
		$bp->activity->track = bp_activity_get_post_types_tracking_args();
	}

	if ( empty( $activity->type ) || empty( $bp->activity->track[ $activity->type ] ) ) {
		return $action;
	}

	$user_link = bp_core_get_userlink( $activity->user_id );
	$post_link = '<a href="' . esc_url( $activity->primary_link ) . '">' . esc_html_x( 'item', 'Default text for the post type name', 'buddypress' ) . '</a>';

	if ( is_multisite() ) {
		$blog_link = '<a href="' . esc_url( get_home_url( $activity->item_id ) ) . '">' . get_blog_option( $activity->item_id, 'blogname' ) . '</a>';

		if ( ! empty( $bp->activity->track[ $activity->type ]->new_post_type_comment_action_ms ) ) {
			$action = sprintf( $bp->activity->track[ $activity->type ]->new_post_type_comment_action_ms, $user_link, $activity->primary_link, $blog_link );
		} else {
			/* translators: 1: the activity author user link. 2: the post link. 3: the blog link. */
			$action = sprintf( esc_html_x( '%1$s commented on the %2$s, on the site %3$s', 'Activity Custom Post Type comment action', 'buddypress' ), $user_link, $post_link, $blog_link );
		}
	} else {
		if ( ! empty( $bp->activity->track[ $activity->type ]->new_post_type_comment_action ) ) {
			$action = sprintf( $bp->activity->track[ $activity->type ]->new_post_type_comment_action, $user_link, $activity->primary_link );
		} else {
			/* translators: 1: the activity author user link. 2: the post link. */
			$action = sprintf( esc_html_x( '%1$s commented on the %2$s', 'Activity Custom Post Type post comment action', 'buddypress' ), $user_link, $post_link );
		}
	}

	/**
	 * Filters the formatted custom post type activity comment action string.
	 *
	 * @since 2.5.0
	 *
	 * @param string               $action   Activity action string value.
	 * @param BP_Activity_Activity $activity Activity item object.
	 */
	return apply_filters( 'bp_activity_custom_post_type_comment_action', $action, $activity );
}