Source

File: wp-includes/comment-template.php

function comment_form_title( $no_reply_text = false, $reply_text = false, $link_to_parent = true ) {
	global $comment;

	if ( false === $no_reply_text ) {
		$no_reply_text = __( 'Leave a Reply' );
	}

	if ( false === $reply_text ) {
		/* translators: %s: Author of the comment being replied to. */
		$reply_text = __( 'Leave a Reply to %s' );
	}

	$reply_to_id = isset( $_GET['replytocom'] ) ? (int) $_GET['replytocom'] : 0;

	if ( 0 == $reply_to_id ) {
		echo $no_reply_text;
	} else {
		// Sets the global so that template tags can be used in the comment form.
		$comment = get_comment( $reply_to_id );

		if ( $link_to_parent ) {
			$author = '<a href="#comment-' . get_comment_ID() . '">' . get_comment_author( $comment ) . '</a>';
		} else {
			$author = get_comment_author( $comment );
		}

		printf( $reply_text, $author );
	}
}