Help discourage repeat abuse offenders who, when their account is suspended, create another account to engage in the same behavior. Perhaps differentiating between normal user behavior and troll behavior can help fight abuse. How does their behavior differ? Perhaps how long they have been on twitter, the number of followers they have and the amount of tweets could be a factor.
Why not have an option (a box you could tick) that could filter your @replies to firstly the people you follow and/or have an option to filter @replies to people who have a lot of followers or whose tweet has been favorited/retweeted many times. Twitter users who have a lot (or even some) followers are less likely to be trolls, are more invested in the twitter community, and are more likely to want a productive and healthy dialogue. This feature will help engage public figures to be more active in the twitter community.