[Stone Mill]

There are some actions which are quite deplorable, however; like:

secret pre-arranged alliances before the game

Something else I find hard to forgive is purposefully exploiting some weaknesses of the game engine with deception, like agreeing to a tech trade (against humans) for tech you do not actually possess, in return for tech. The game will let you do it... but I won't generally trust that player again. I consider that pretty dirty. But it's acceptable.