I agree that email/list is better for the reasons Andreas listed...
However, one issue (pro and con) with the mailing list is that posting has a barrier-to-entry with the knowledge that your are broadcasting to many people. This is great for avoiding trivia, and keeping the signal-to-noise ratio high...
But it might be good to have a place for more trivial or narrow-audience topics. So people can banter about their projects or problems they encounter which they don't deem worthy of trumpeting "Here ye! Here ye!" for. Sometimes I want to waste some time reading about OCaml stuff... but reddit and email have nothing new. :) But I'm also glad these aren't choked with random crap either. A forum-like format reduces the wideband-broadcast, providing some compartmentalization, and the step for a reader to actively go looking. And if something important/interesting to the wider community flares up in such a place, *then* it can be referenced on this list, or reddit.
I, too, would not want to fragment this tiny community. But we seem to lack a place for more voluminous banter, which might have the opposite effect: of livening things up.
I'm not arguing for Discourse necessarily (I haven't looked into it at all), but in general: that a forum might be a useful part of community-building. Or do we have something already which I've missed?