Due to a bug with the software, you are required to post non-bumping comments on deleted images if you wish to comment on them. Just click the box next to the submit button. This is because the image will then show up in comments. If you intentionally bump a deleted image to get it in the comments, you'll earn a nice gold plated week ban. Comments on deleted images may be deleted without notice. Don't exploit bugs. ComradeCosmobot will have to fix the comments page issue at another time.
Hope this helps!