I think that Orthaic's point was merely that whatever goes on in the global chat (or private chat) is "in-game". If there is a serious accusation to make, you must contact the mods. Otherwise, anything goes.
I've had reasons to think, in one game, that 2 players were probably allying and meta-gaming. Had no real evidence to that effect though, so I never made it official by writing the mods. Having said that, I did hint on the global board that such might be the case, hoping to collect a few allies from doing so (afterall, a juggernaut was forming and I was going to use any diplomatic means to make sure it wouldn't be an issue for me). I have to say, it worked! And when one of the two players I was "accusing" of meta-gaming wrote me saying that he really didn't know the other guy, I diplomatically apologized, gave him my reasons and made sure he was written off the map!!!!