We won't hand over personal information without a proper warrant or subpoena.
But understand that people put all sorts of private information online (not just here). An investigator can easily join A2K just like anyone else. There's absolutely nothing stopping them from clicking on a username, looking up all that person's posts, and taking numerous screenshots.
That doesn't need a warrant because you or any other member can do that, assuming you had no life and felt like wasting your time that way. The main thing stopping law enforcement is that it would be time-consuming and expensive.
Compared to Facebook, etc., A2k is a rather small fish. A much, much better use of the law enforcement/DA budget would be to serve FB with a subpoena.
As for whether the administrative team has ever been served with a subpoena or warrant, I will never tell you. Because if anyone ever has, they are entitled to their privacy, now, don't you think?