(Trying out Branch - let's see how this goes for discussion)
As with so many aspects of games, it's all about the motivation. Why does the city exist? Is the main selling point of citizenship the roleplaying and collaborative fiction, or other types of fun (collecting, combat, levelling up). Obviously, the first kind has the motivation for staying in-character built in. But even then, teaching new citizens what "in character" actually means can be a long process. There's more value in working out how to keep the atmosphere without relying entirely on the players, or at least allowing it to survive a percentage of misfits.