Some suggestions from Caroline Sinder on how to limit abuse on Twitter. Interestingly these settings are close to the sorts of things we used to use in political communities to limit abuse, using time on site and connections to others as proxies for the troll/not-troll decisions.
Some of these issues helps stymie trolls, but remember that abusers are Not Just the Trolls
Pew has a 2014 report on abuse on the net. (Link)