I added password protection to the RSS 2.0 feed for comments and checked it in. You can subscribe to the feed directly (http://www.example.com/wp-commentsrss2.php) to get the latest comments, or pass in the post ID and subscribe to comments for that particular post (http://www.example.com/wp-commentsrss2.php?p=1234).
I also added password protection to the pop-up comments page (b2commentspopup.php). If you see anywhere that does not use the password protection let us know about it.