That's your prerogative of course, Matt... but if you set up a "community", the social BS goes hand in hand with it. The internet's rife with it!
Although it's not as bad as it used to be... Nobody's threatened to stab me for years!
Every time someone tries to pull someone else up on here over something, there's either a bunch of dummy-spitting goes on or the thread's deleted.
So it's not really surprising that some unhappy people have taken to sending you PMs. They probably feel there's no point in saying anything on the forum to the people concerned, as it'll just get deleted.
It's got to be better to receive a few complaining PMs than to have a mass exodus and consequently a loss of revenue?
I'm not saying you shouldn't delete contentious threads, necessarily. I understand that we want the forums to remain welcoming to new members and lurkers, but it's a logical conclusion to make that members will then contact you or the mods directly, instead of bringing it up on the forum.