Let me know if you need help with any of these. They probably require less than 20 minutes to implement.
1.) I just posted a comment with a typo, but I could not correct it, so an edit feature, or at least a preview feature before you submit the comment would be helpful.
2.) A bigger box to write these comments! I find these one line comment discussions very confusing, and I wonder if they would be limited if there was a bigger comment box (I am already getting a scrollbar with a comment this long).
3.) Some way to see posts that have drifted off the top and new pages. Someone told me about a post that apparently just got knocked off one of these pages and I can't get it. This is a complicated feature request because I really do like only having to look through a couple of pages to see what is new (a real plus on the simplicity side). But not being able to find a good post that someone sent you is not good.
4.) A 'track-this-discussion' feature. I am sure you have something like this in the admin console for the site. If there is a really long discussion that is a few days old, and someone posts a reply to my comment, odds are I am not going to see this reply unless I am very vigilant on that page. I think some sort of tracking or alert system (of course optional) would be nice so that you will be alerted (emailed or possibly some sort of user message in the top right corner when you log in). Se mediawiki's 'Watch This Page' feature.