I will reply to the rest later but for now I just want to come back on your comments about moderation and communities, which I agree with. The question I have, though, is whether these are actually communities? Most users treat them like this - but is that what the government (or Hansard) wants? While they have no policy influence they do little more than bring some people "closer" to each other and this has democratic output benefits in terms of Habermas and the public sphere. And thus the Community side is important. But if we are to use such fora at a policy level then we want "serious" contributions and for these not to be dominated by a small minority. I guess it is possible to have both at the same time.
I've read quite a bit about MUDs but as a supposed political scientist I've never written about them. Though I am becomming more and more sociological so who knows! The Marc Smith book has a great chapter on this....