default callback function in wp_list_comments May 30, 2022 by Tarik Billa The wp_list_comments() function uses the HTML comment list class Walker_Comment by default: A single comment is then displayed with the Walker_Comment::comment() method (#source). If the comment format is HTML5 then the Walker_Comment::html5_comment() is used instead (#source). The pingbacks are rendered with the Walker_Comment::ping() method (#source).