Our default setting were wrong (admins, it was under admin>content types>forum topic, quick search on drupal.org told me all I needed to know). So all the older forum topics are locked. I'll go through and unlock them (ahhhh yeah... repititive and boring. Why I love being a webmaster!) and new topics should allow comments by default. Sorry! This kind of thing is why we haven't really promoted the new site yet.

-Rafael