Restrict game to 1 account / server. :D I bet, people will treat their account with extreme care, won't flame so much, won't troll, won't do all the things we know they do, just because they are either smurfing, or they don't care beacause they have another account, or various reasons. If this step wouldn't drasticaly reduce the number of trolls I don't know what would.
And there are so many modes to play this game, that you don't really need a smurf account, to "try things".
However :D I know they will never implement this 1 account/server, since it would be a financial disaster, no more new accounts to buy skins and whatever else, people who get perma would have a harder time to play again.
Still :D i can't help but wonder, if this move would be as effective as I think it would.