I take part in a large and popular writing site, where they pretty much enable users to write and create anything possible within the realm of writing. This includes things like 'mad libs' or surveys or 'add a line'.

Some of the terms to describe various items are:
sliders
In and out
Interactive story
Campfire (something, I don't remember)

Some terminology that might branch off one of these or a similar phrase or idea might encompass all that can go in that forum, not indicating that the subject matter is necessarily serious or amusing or anywhere in particular in between.

If the point to get across is that the threads are highly interactive, maybe something like coffee house, lounge, etc... I'm not even sure.

But both of those places are neutral- people go to meet and engage and exchange but the particular atmosphere tends to be dictated by the people in them, not the space (like the games board... I think?)

I hope I am understanding the issues at hand. I apologize if I'm not getting at it quite right.

Anyway, just a couple of ideas.