I'm the current maintainer of PerlUnit, and a newbie to wikis (it probably shows).
My homepage: http://tigerpig.org/
I'm fascinated by wikis' potential as vehicles for information exchange. However, I don't like that the ThreadModeConsideredHarmful problem is still unsolved, and that wikis apparently favour DissertationOverDiscourse. I think that with a few small adjustments, wikis could be an excellent home for threaded discussions.
I see that other people have proposed node pairs as a potential solution to this, where every node in DocumentMode can have a corresponding ThreadMode node (DiscussionVsConsensus). My proposal is slightly more involved: that when you wish to discuss a node, you initiate a series of discussion nodes, which are all automatically threaded by the wiki software. Each discussion node would map directly to a post in a mailing list or a newsgroup, and would be AppendOnly (in practice, pretty close to ReadOnly? in fact). The wiki engine would recognise a node as being a discussion node which needs to be treated specially, and hence would automatically generate all the usual "in reply to", "post a reply to this" etc. type of links which you see in standard mailing list archives or Google Groups.
A nice pro to this approach is that you get the equivalent functionality of an unlimited number of mailing lists, without any of the administrative hassle normally associated with them.
I'm aware that this kind of enhancement goes against the grain of the KeepItSimple philosophy behind the c2.com wiki. Maybe it would be worth trying as a plugin for TWiki.
I'm also aware that suggestions like this probably don't belong on personal pages. I've just put it here as an experiment to see what kind of responses I get :-)