First, for at least this past decade, I have found it impossible that the same user will keep the same IP address for over two months. Storing the IP address _d

First, for at least this past decade, I have found it impossible that the same user will keep the same IP address for over two months. Storing the IP address _does not help at all_. Second, the new user is subject to approval and all his messages are moderated until a couple of posts. If he starts posting decent material, why would you care he was banned 2 months ago -- are you really that punitative? And if he just posts decent, insightful material for his 5 messages, gets approved and then descends back immediately into trolling, well, at least it's been a couple of months and then the couple of weeks he was under moderation of total silence, plus you have gained whatever contributions he made under moderation. I am yet to see a troll that will repeat this process (which requires insightful contributions in-between each iteration of trolling) for more than a year. That's way less moderating effort that it takes to handle new users at all...