Reply to comment does not load custom editors for text field

PHP 5.2.8 on a 1and1 LAMP host; tested with Firefox 3.1 and IE 8. The site is gaw.warshaft.com; please feel free to create a user and test there if you like - although additional modules are now enabled on that site again, since I can get no further with attempting to find the root cause of this issue.

To reproduce, install an editor module such as BUEditor or WYSIWYG API + TinyMCE. I tested with both BUEditor and TinyMCE, and all other add-on modules disabled.
Create a forum post, then "reply" to that forum post. Likely this can be done with a reply to any comment.

I'd expect the textarea "Comment:" to display the editor controls. Instead, it uses the default editor without additional controls.

I noticed that this happens only if ?q= contains a "#" after the url, to jump to the comment-form, like this: "?q=comment/reply/15#comment-form"

Reloading the page as "?q=comment/reply/15" will show the editor.

Likewise, hitting "Preview" or "Save" on an empty comment field will reload the page without the "#comment-form", show an error "Comment field is required.", and show the custom editor on the "Comment:" textarea.