$filter

apply_filters( $filter, '<a href="' . $link . '">' . $text . '</a>', (int)$total_items )

messages_format_notifications

do_action( 'messages_format_notifications', $action, $item_id, $secondary_item_id, $total_items )

do_action( 'messages_delete_thread', $thread_ids )

do_action( 'messages_before_delete_thread', $thread_ids )