From what I can surmise, the difference between ZLMB and FAIR was one of "control". She wanted a place that she could have more control over and that was not a possibility at ZLMB. I could be wrong, as I've said, I was not on ZLMB so I can only go by what I have heard and what I have seen at FAIR.
I'm sure there were many reasons why others choose to leave ZLMB and go to FAIR that were legitimate. Capping posts would make the board slower but couple that with an exodus of main contributors and even those who chose to stay would find themselves pretty lonely after a while.
She does have quite a bit of influence and control at FAIR. I know she heatedly denies it, but I know from private emails from those "in the know" (but not quite pleased with the situation) that due to her position as one of the founders plus a source of funding, that she has quite a bit of say-so. Of course, anyone can figure that out quick enough. The first time I ever posted on a FAIR thread, she repeatedly called me a liar and a plagiarizer without the slightest justification. The only consequence was another moderator going behind her editing out the insults. I knew at that moment, given our history from Z, I would not last long on that board. (and was eventually banned, and I'm quite certain that was upon her specific request, since the mods initially did not take action against me regards her silly complaint and then suddenly Scott swooped in and over-rode the mods and banned me)
You're also right that she definitely had no control at Z. Despite the fact that two of her very close friends were moderators, they were always careful to either let their personal bias at the door, or sometimes even recuse themselves from decisions regarding her. She was treated just like any other poster, behind the moderator door. (of course, I'm talking about pre-exodus, when there was more active moderation in general and the "no bias" guideline was still being applied) And you can imagine she did get "dinged" regularly, given her pattern of posting. I really don't remember DCP being treated preferentially when I was mod, either, but perhaps that was during his less active phase, I can't recall if he was around much when I was mod. The only poster I ever witnessed preferential treatments towards was, oddly enough, Pahoran, due to the board owner's long association with and affection for him. That does not mean that we wouldn't "ding" Pahoran and even ban him for short periods, but any other poster with his track record would have been permanently banned long ago, and pac, by his own admission, just couldn't bring himself to do it. He'd agree to ban him for three months, and expect "good behavior" upon his return. He'd be good for a while, but would slide back into the old routine. I have never hid the fact that I felt this was a problem for the moderating team at Z, because as long as others saw Pahoran getting to come back after such bad behavior could be less inclined to take the rules seriously. But as far as I remember, everyone else was treated without bias.
I don't think that is the case, anymore, however, as the recent treatment of Shades and Jersey Girl demonstrate.
I do think that one thing FAIR changed was openly admitting to giving preferential treatment to those whom they regard as significant, scholarly posters, like DCP. They desperately want to keep those people aboard, but I'm not convinced they've succeeded. Perhaps I'm not reading the right threads, but it seems to me that people like Ben McGuire and Brant Gardner rarely post over there, to say nothing of Brent Metcalfe.
Running internet boards is a tough job. While I have repeatedly stated that I don't want to post at MAD because of the pre-poisoning of the well that goes on against critics, in addition to the biased moderating (I just don't have the time or the will to think twenty minutes about every sentence I write to make sure I won't possibly offend a believer, and I think that's a patronizing attitude to adopt towards believers anyway - they ARE at a board to discuss these issues, right?? They're big boys and girls.) - I also state that they have the right to run their own board however they want. I also have the right to point out the hypocrisy behind how they run it, and choose not to participate.
Having said that, I'm still unconvinced that it's even possible to have a decent LDS/exLDS board. It's hard to have a decent board of ANY type on the internet, much less about such an emotionally laden topic. Internet boards seem either to end up being too slow and too small to generate interest, or growing to a point that generates movement and interest, and then getting all these "behavioral" issues to deal with. It doesn't take too many vocal bad apples to make the whole barrel appear rotten (as I think happens quite a bit on RFM, too).