[gfodor]

You can cut off a large part of abuse by just creating a financial based incentive. Pay to gain access, and access can be revoked at which point you need to repay (perhaps on a progressive scale - ie the more you are banned, the harder it is to get back in.) Your identity confers a reputation level that influences filters so what you post is seen more often, so there is value in your account and you don't want to lose it. The SA forums did this and it helped immensely with keeping out spam (though not a silver bullet.)

Any system where any rando can post any random thing with no gates is going to be much more of a slog to moderate than one where there are several gates that imply the person is acting in good faith.