You can show any PM to anybody you like. You can't post it on one of the public forums without the author's permission. Of course, it might be very rude to show somebody's private PM to another party without their knowledge or permission, but that's a matter of upbringing, good manners, that kind of thing. Is this really so hard to understand? I can't speak for "most" admins. As an admin here, I can tell you that I have no power to read people's PMs. Only the site owners can do that, and I'm sure they would only do it if there was a good reason to do it.