There is another factor that nothing to do with the board culture itself (which is a fantastic zone of free inquiry—thanks Dr. Shades!).
The most active posters, from what I can tell, I have been here for some time, and it seems to me that most posters here are Gen X and older. That is the generation most impacted by the Internet's snare of Mormonism. To me, a message board was alien architecture in the age of Reddit and Youtube, and it was quite happenstance that I found this place; even then it took a few years of lurking before I first posted. I would consider even Facebook to be old-fashioned at this point. The short of it is: I wonder whether this board is having or will have trouble replenishing itself because, with all due respect, it feels like a relic from 1999. That is kind of what I like about it. It encourages long-form discussion (threads that go on for dozens and dozens of pages), and that tends to bring out some really excellent posts and posters that I have enjoyed reading over the years and have been lucky enough to engage with at times. But that is completely antithetical to internet culture. There is a certain degree of snark here, but it's hard to sustain interest with that alone. Moreover, there is very little appeal to the self-esteem lizard-brain that drives so much of places like Twitter and old Facebook (no like buttons or retweets and ____ that like). So it is hard to draw in users attracted by the ephemeral entertainment of social media.
But who are those users? They are mostly younger, and, as I've argued here endlessly, they/we do not care about the aspects of Mormonism that motivate GenXers. We millennials, who all suck, mostly have just faded away from Mormonism and don't care or even know about the Book of Abraham issues (sorry Shulem). I didn't even learn about them until after I quit going to Church when I was a student at BYU. Church was boring, stiflling, and obsessed with uniformity, and that was enough for me to say "no thanks." I didn't need to prove to myself that the Church was incorrect on matters of Meso-American archaeology or Egyptology (also, I never took a lot those claims that seriously either). My suspicion, based obviously on anecdote, is that it is even more the case with people born in the late 90s and early 2000s. What is there to discuss for that kind of demographic? The Church's social stances are much more of an issue, but they are not an issue for discussion but merely an easy grounds for rejection.
Some people will just be interested in the topic (like me), but that's quite different from the period in the late 90s and early 2000s when all these GenXers who had grown up hearing a version of FARMS in Church suddenly discovered Richard Packham's site or things like that and had their worldview start crumble. From what I have learned from some of you hear, I would guess that a lot of GenXers saw that older form of Mormonism before it was completely subsumed by the weird corporate culture and where doctrine—that is, truth claims—still mattered. Challenges to the Church's truth claims, particularly those based in evidence, were taken so seriously because they had such deep implications. For people like me, though, who mostly just heard about the evils of porn and saw the doctrinal people treated as total weirdos by the bishops and such, truth claims weren't the central issue. The central issue—that being Mormon was just boring and dumb with no perceptible benefit—is not one worth discussing because it's solution is obvious: stop being Mormon. Huge swathes of my generation and the following have taken that route. Also, even GenXers tend to move on at a certain point, and as people start orienting their lives without Mormonism at the core, their resentment, frustration, and preoccupations with their Mormon experience start to fade.
Peterson-mania is more noticeable of late perhaps because, when it comes to Peterson, this board behaves almost like a Twitter thread where the offending Tweet is screenshotted but not linked to: he says something over there on his blog, which is reported here, and then people comment over here. It also provides some posters satisfaction, perhaps. So it is an activity that in part replicates what his happening elsewhere in Internet culture, but the fact that it is about Peterson also imbues the whole thing with nostalgia, since a lot of the people posting about him talk about a time when he was here (I wish I could have been here for those discussions!).
PS. To the assumption above that the Church will sink to an activity rate of 40% as if that were a bad thing, I would invite readers with an interesting to peruse one of the talks of Ezra Taft Benson from the late 50s or early 60s available on BYU Speeches. It's been a long time since I listened to them (because I do think they are very interesting historical artifacts), but in one them Benson recounted to his audience one of his many discussions with leaders of other Churches. In that discussion, Benson bragged about the activity rate of the Church, which the Protestant clergyman could not believe: it was around 40%! So Benson in the 1960s or late 1950s thought that number was a good one. I am inclined to agree with Huckleberry: 40% activity rate is just fine if they no longer depend on that group for their financial basis. With $100 billion cash, the Church leadership can ignore wet washrags like Uchtdorf and hammer on the doctrine again, content to jettison any pastoral approach to the disaffected because the truly elect will self-select.
"As to any slivers of light or any particles of darkness of the past, we forget about them."
—B. Redd McConkie