There are plenty of communities that mitigate this problem through earned privileges. Real users who are participating in the community are able to do more than someone that just signed up with a throwaway address. Stackoverflow seems like an okay model... recent moderator issues aside.I'm scanning my memory banks and Stackoverflow is the only "earned privilege" community that comes to mind and my experience with it has been uniformly unpleasant, let's say "bordering on toxic". If anything, automatically earned privilege creates competition which makes everything worst and nastier.
In contrast, I moderate a medium sized FB group in a topic that often has trolling. We eliminate it entirely through hand-picked moderators and a zero tolerance statement. There's no competition to be a moderator and there's actually little for the moderators to do since making things clear mostly works. So there's no competition for anything and people spend their time discussing issues instead.
HN seems to be closer to that situation also - with karma hidden, competition is pretty limited. And anonymous posters can make fine contributions here.