...If more communities on the web could just be more like here...
I suspect you hit the nail on the head there by use of the word "communities". I think it was the Bell Hawthorne Labs workgroup experiments in the '50s that showed pretty conclusively that a workgroup community will tend to generate its own collective ethos - i.e., the characteristic spirit of the community as manifested in its attitudes and aspirations.
One of the conclusions was that, whilst one can dictate formal rules, the group will find its own vector and rules regardless and may even informally overturn any formal rules set that it does not agree with.
To avoid this, @mouser's
approach, coupled with a strict diversion of irrelevant (to the forum) or flameworthy discussions to the private Basement area probably ensures that the forum is controlled and the community cannot hijack it and alter the ethos. The forum thus retains an air of being very much "@mouser's
front room", and people seem to respect that.
It seems to be a fairly straightforward approach to maintaining a public focus on what matters to the forum, and because the forum does not necessarily condone or agree with what goes on in the Basement, the robot.txt file blocks crawlers, so the Basement content can never appear in searches or the Wayback machine and is thus effectively expunged.
Any problems or issues arising in the public forum otherwise seem to be managed adequately by admins or forum members putting people straight.
The result is arguably a relatively stable, well-focused forum, and at a personal level the donation aspect probably tends to give a subconscious feeling of individual personal buy-in and commitment to the community, amongst DCF members. It seems to work.