I've played on and off for over a year now and the game has obviously gone down hill troll wise. Instead of forcing players into one lobby with some troll; there should be a setting that allows players to pick between lobby 1,2,3, ect. This way 13 people don't get held up by 1 troll who constantly invites the same person that constantly declines after like 2 minuets. If possible it would also be a good idea to just make a trolls only lobby. Like mark their accounts with something that requires them to join lobby x when playing mafia. I am assuming banning them from joining the game itself is impossible but the game is probably screwed if something isn't done.
Side note: Banning someone for leave trains is pretty pointless. It just means they take up a slot and will get kicked which causes leave trains... It's not like they had any intention to play the game to being with.