lib/notifications/notificationemaillib.php

    // Users watching this forum or this post
    if ($prefs['feature_user_watches'] == 'y' || $prefs['feature_group_watches'] == 'y') {
        $nots_raw = $tikilib->get_event_watches($event, $event == 'forum_post_topic'? $forum_info['forumId']: $threadId, $forum_info);
        $nots = array();
        foreach( $nots_raw as $n ) {
            if( $n['user'] != $author ) {
                $n['language'] = $tikilib->get_user_preference($n['user'], "language", $defaultLanguage);
                $nots[] = $n;
            }
        }
    }