If you set the (hidden) static field in the comment form to a URL (for post-submission redirection), MT assumes that you want to append a '#' and the comment id onto the end of the URL. Not only is this a false assumption, but it also creates anchors like '#122' which is not XHTML compliant and hence (with the default templates or anything more strict) is unusable.

The code is found on line 122 (version-dependent) of App/Comments.pm:
In my opinion, it should either be changed to:
Or, perhaps better:
The latter would allow someone to better craft the redirect URL if it was necessary. For instance:
In case you are wondering, the reason that I am putting a URL in the static field (and using all of that crazy PHP) instead of just putting a 1 (which would normally just return the user to the individual entry) is that the blog in question publishes to TWO different domains. I pubilsh two sets of archives for each archive type and the Archive File Template for the DOMAIN2 archives looks like '../DOMAIN2/etc/etc'.

If I just used '1', the redirect URL would be:
...and that is obviously no good...

Anyhow...