On a side note, I do think that the forum format has the advantage of very clearly delineated categories/sub-forums, which can help set expectations to an extent. When one goes into the DnD forum, for example, one can reasonably expect discussions of DnD, which, like all systems, has its own set of core assumptions, problems, and values. And, since I rarely have anything nice to say about DnD, I would likely not spend much time in there (except for moderation purposes, obviously). Participants should of course still always try to avoid stepping on toes, but at least they can be aware of the parameters of their discussion based on where they are posting. Now, I definitely don't think we can solve the whole issue simply by keeping things on topic by category (and this forum is not currently active enough for all of those categories to get much play), but that is still something we can take advantage of.
I can't create new sub-forums at will, but I can ask the good folks at itch if we want to make changes to the structure of the forum. They are generally fairly responsive and quick. So do let me know if there are any categories your think might be useful to have or are missing.