Two things I look for in discussion forums are: recent activity (that's not just a flash in the pan); and that most threads have multiple replies. That second one is very important. Even if there are a lot of posting to a forum, it's not much of a support community if a lot of those posts go unanswered, or with just a single reply. This forum seems to score well on both of those.
Another thing is a non-judgmental approach. To be honest, I'm not here long enough to fully defend this in court yet, but the vibe so far is good. One example is the way that, on some forums, people get jumped on for moving outside what The Forum Gods consider Received Wisdom. Obviously there's space for demanding common sense. If someone claims that their new "drink a gallon of scotch and then tape your mask to your face while gluing your nostrils shut" method is a cure for apnea, then we all reserve the right to say "shush, child!" But on some boards the attitude seems to be that doctor always knows best, and that we should all be seen and not heard.
Finally, and this is probably an example of the openness I've just mentioned, is the provision of CPAP admin control data. The analogy about how we're sensible enough to handle our prescription drugs ourselves is good. Also, the fact that there is now some published science to show that, shock horror, with a modest amount of education we apnea sufferers *can* actually self-titrate in a way that improves wellbeing. So VERY WELL DONE on that.
Whoever is running the show (but also to the various keen members who all make up "the culture"), kudos and many nights of deep and restful sleep to you dude(s)/dudette(s)!