Option to make WordPress comments private

/**
* Make comments able to choose private or public...
* as seen in http://wpquestions.com/question/showLoggedIn/id/10468
*
* TERMS: a 'comment' is a comment to post. a 'reply' is a comment to a comment..
* scenarios:
* 1. a comment can be public or private. checkbox is visible.
* 2. a reply can be public or private based only on the following (no checkbox):
* a. if comment is private, all reply are automatic private.
* b. if comment is public, all reply are public.
*/
function restrict_comments( $comments , $post_id ){
global $post;
$user = wp_get_current_user();
if($post->post_author == $user->ID){
return $comments;
}
foreach($comments as $comment){
$is_private = is_comment_private($comment);
if (!$is_private ) {$new_comments_array[] = $comment;continue;}
if( $comment->user_id == $user->ID || $post->post_author == $comment->user_id ){
if($post->post_author == $comment->user_id){
if($comment->comment_parent > 0){
$parent_comm = get_comment( $comment->comment_parent );
if( ( $parent_comm->user_id == $user->ID ) ){
$new_comments_array[] = $comment;
}
}elseif (!$is_private){
$new_comments_array[] = $comment;
}
} else {
$new_comments_array[] = $comment;
}
}
}
return $new_comments_array;
}
add_filter( 'comments_array' , 'restrict_comments' , 10, 2 );
function is_comment_private($comment) {
$is_private = (get_comment_meta( $comment->comment_ID, 'private', 'no' )=='yes')?true:false;
if ($is_private && !($comment->comment_parent > 0)) {
return true;
} elseif ($comment->comment_parent > 0) {
return is_comment_private(get_comment( $comment->comment_parent ));
}
return false;
}
add_action( 'comment_post', 'save_comment_meta_data' );
function save_comment_meta_data( $comment_id ) {
if ( !is_user_logged_in() ) {return;}
if ( ( isset( $_POST['private'] ) ) && ( $_POST['private'] != '') )
$private = wp_filter_nohtml_kses($_POST['private']);
add_comment_meta( $comment_id, 'private', $private );
}
add_action( 'comment_form_logged_in_after', 'additional_fields' );
add_action( 'comment_form_after_fields', 'additional_fields' );
function additional_fields () {
if ( !is_user_logged_in() ) {return;}
echo '<p class="comment-form-private">'.
'<label for="private"><input id="private" name="private" type="checkbox" value="yes" />' . __( 'Make this comment private' ) . '</label>'.
'</p>';
echo '<p class="comment-private-msg">Please note: Your reply will be private</p>';
echo '<p class="comment-public-msg">Warning: Your reply will be public</p>';
}
add_filter( 'comment_class' , 'private_comment_class',99,3 );
function private_comment_class( $classes, $class, $comment_id ){
$is_private = is_comment_private(get_comment( $comment_id ));
if($is_private) {
$classes[] = 'private-comment';
}
return $classes ;
}
add_action('wp_head','add_css_style');
function add_css_style(){
?>
        <style>
                .comment .comment-form-private,
                .comment-private-msg,
                .comment.private-comment .comment-public-msg,
                .comment-public-msg {
                        display: none;
                }
                .comment .comment-public-msg,
                .private-comment .comment-private-msg{
                        display: block;
                }

        </style>
<?php
}