I have just dropped into the 'Site & Forum Feedback' section to report this precise matter; in my case, the desktop version of the site barely fits (actually it spills over the edges of) my 13" MBA screen ..
Hm.. Thanks for starting a thread - I wasn't even sure quite what terms to use to describe what I noticed had happened.
I'm on my 27" iMac right now and its doing the same when viewing threads.
I'm assuming Arn is doing some work on the site right now and this will be cleared up soon.