fembooru/themes/default/comment.theme.php

<?php

class CustomCommentListTheme extends CommentListTheme {
	protected function comment_to_html($comment, $trim=false) {
		return $this->rr(parent::comment_to_html($comment, $trim));
	}

	protected function build_postbox($image_id) {
		return $this->rr(parent::build_postbox($image_id));
	}

	protected function rr($html) {
		return "
			<!-- cancel border -->
			<div class='brr'>$html</div>
		";
	}
}
?>