There is meta-gaming and then there is metagaming. If players carry into the game pre-conceptions of other players derived from earlier games, this is in a sense meta-gaming. But this type of meta-gaming is not cheating. At worst it results in sub-optimal play (although I concede it can have its advantages at times).
The more pernicious type of meta-gaming that is defintiely cheating is where one deliberately forms alliances before entering the game, such as room-mates, for example, who join a game knowing full well that they will ally (even if they agree a stab at some point is on the cards). This is wrong. Even worse are players who form unbreakable alliances with the intention of harvesting points, by taking turns in taking the win, or by going for the 17/17 draw. This is definitely cheating.
I don't think DoctorJingles has said the he is guilty of this bad kind of metagaming. He has not said that he is cheating. His style of strategy of trusting players based on previous games is not one I would choose, but I don't think it is out of bounds. He can play the game however he sees fit, like any other player, just do,long as he does not cross the line.