AFAIK, there have been some members that have been banned before for trolling. One of them was the Bitcoin Satoshi Vision guy, and then I also remember game-protect. Here is what I think why action might have not been taken yet;
1. Maybe no one has yet reported him to the moderators about his trolling
2. Maybe someone has reported but hasn't made an extensive report showing how he has been trolling around over time
This is what I saw in the FAQ
Q: Do you moderate/delete (possible) FUD, accusations and untrue information?
A: No. We don't have enough time to check every single piece of information and verify the validity of the sources. Also, just like scams - too much room for bias and abuse.
However, trolling isn't allowed. If a user is habitually posting obviously false nonsense ("obviously false nonsense" to an outsider, NOT to someone who follows or is involved in the discussion) just to stir up trouble, then it's considered trolling, which is prohibited. Such cases should be thoroughly documented in the report though (There are tons of reports that just say "trolling", but moderators don't have time to look through each user's post).
