Post Author & commentor privacy

Only post author and commentor can view each others comments. Works as a great private message form!

// http://wpquestions.com/question/showChronoLoggedIn/id/10125
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){
	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;		
				}
			}else{
					$new_comments_array[] = $comment;	
			}
		}else{
			$new_comments_array[] = $comment;			
		}
	}
}
 return $new_comments_array; }

add_filter( 'comments_array' , 'restrict_comments' , 10, 2 );