I think this may be due to the super-secret changes...
I'm using Firefox 1.5.0.6 on MacOS X.
When I post a comment, it
is successfully posted, but instead of the page reloading with my comment showing up, I'm shown the comment posting form again, empty, with red text telling me the comment text is required, and the thing I'm replying to beneath it.
It looks like this:

What gives? :)