I toyed with the idea in @Sparkles thread (a "good character" room) but for it to genuinely filter trolls and smurfs, I think you'd need manual evaluation of character as well as time served. In other words, the whitelist would need to be managed by someone with access to reports submitted to moderators to decide if this person really is well behaved enough to be trusted in a room with standards. You'd also need a record of play against other people evidenced by reaching a certain level. Sure it could be gamed, but if it takes, say 20 hours of multiplayer to get a smurf to look fit for the whitelist, that's a lot of effort to go for being able to spoil one game before being locked out forever. Without the ability to locate the troll in real life and hold him personally to account, all we can really do is raise the level of effort required to the point it's not worth it.
The more important objection though, is the one room culture already highlighted. I only proposed the good conduct room as a potential addition to a new world where the default team game is a no-elo, no consequences, no standards (except reasonable manners) lobsterpot with serious rooms for serious players to migrate into if they don't want to just mess around. The lobsterpot would have to be no-elo in order to ensure that serious players felt freer to drop it half way through if there was actually critical mass for a serious game.
