Ugh. There was a lot of discussion about how to reduce the unfairness of this.
Guess the devs didn't have the time, which is actually understandable considering the amount of posts etc.
Here's three simple rules that is reasonably fair and almost un-abuseable.
-Leaving the game before a specific amount of turns (amount of spaces, not turnframes) doesn't give you an ELO penalty.
-When a player executes a command that gets a player out of the game, the penalty should always lie on the one who executed the command - if an op fspecs you the penalty is on the op, if you spec yourself the penalty is on you. This applies as long as it doesn't conflict with rule #1.
-Quitting and pinging is regarded in the same way, an ELO penalty for the one who quitted or pinged. If a player goes afk pre-game no penalty is given. If two players quit, ping, or go afk at (roughly) the same time, no penalty is given. This applies as long as it doesn't conflict with rule #1 or #2.