A couple tiny suggestions
In the vein of your "Forum quality is predicated by good UI / layout" talk I have a couple of suggestions:
1) Remove the "X.X k views" and "Y.Y k comments" vanity metrics from the discussion listing. They are just clutter and serve no purpose.
2) Remove the avatar of the original poster from the discussion listings. This is also just a vanity feature and is even detrimental to the user experience. I don't want to know that Rym started this discussion chain in 2007, I want to see who the most recent commenter is (preferably I would like to see the most recent three).
These suggestions are, of course, matters of opinion, but I think they are reasonable ones.