function separate_comments( &$comments ) {
	$comments_by_type = array(
		'comment'   => array(),
		'trackback' => array(),
		'pingback'  => array(),
		'pings'     => array(),
	);
	$count            = count( $comments );
	for ( $i = 0; $i < $count; $i++ ) {
		$type = $comments[ $i ]->comment_type;
		if ( empty( $type ) ) {
			$type = 'comment';
		}
		$comments_by_type[ $type ][] = &$comments[ $i ];
		if ( 'trackback' == $type || 'pingback' == $type ) {
			$comments_by_type['pings'][] = &$comments[ $i ];
		}
	}

	return $comments_by_type;
}