I think you're asking a good question and that was the thrust of 'olddog's' (I believe it was) question too. It appears to me, forums take on a certain "personality" - for lack of a better term. Based on their owner's motivation and desires for the forum, how topics are handled and discussed, tend to determine the relative success of a forum. As the forum grows, the selection of moderators becomes critical - usually they need to reflect the owner's values and desires for the forum.
I've posted a meme before, in one form that got about 27 gazillion "likes", only to post the same meme in a different forum that got immediately deleted and resulted in me receiving a nasty-gram from a moderator. I made a personal decision to withdraw and discontinue my participation in that particular forum. To me, each forum has to decide the level of strictness and tolerance it's willing or desires to impose. It's their call; I think it can be a very "fine line" to make such judgment calls.
The same holds true for exactly how "freewheeling" discussions within a thread are allowed to be. (I tend to like the forums that allow a fairly wide latitude - as long as it stays half way civil). Wondering from the thread topic usually corrects itself (eventually). [emoji6]
I've only seen probably less than half a dozen threads 'shut down' by moderators in all the time I've been reading forums. And I'd say, that was the right call to make on the part of the moderator. The discussion(s) had turned pretty nasty and shutting down the thread allowed for 'cooler heads' to prevail.
How much the "personality" of a particular forum matches your own, I think, goes a long way in determining how much you enjoy and will participate in that forum.