rearrange_comment_form_fields.php

<?php
/**
 * Changes order of comment form fields for anonymous users. Rating form items first, followed 
 * by comment, author, email and url. Note the comment_form_fields filter is only available since
 * WordPress 4.4
 * 
 * @param array $fields
 * @return array $fields
 */
function my_comment_form_fields( $fields ) {
	
	$comment = $fields['comment'];
	unset( $fields['comment'] );
	array_push( $fields, $comment );
	
	$author = $fields['author'];
	unset( $fields['author'] );
	array_push( $fields, $author );
	
	$email = $fields['email'];
	unset( $fields['email'] );
	array_push( $fields, $email );
	
	$url = $fields['url'];
	unset( $fields['url'] );
	array_push( $fields, $url );
	
	return $fields;
}
add_filter( 'comment_form_fields', 'my_comment_form_fields', 100, 1 );