When we ban people right now all their posts are deleted. This screws up threads where they've posted in, to the detriment of those threads.
This means the more a user has posted on the site and, particularly, the more they have posted in threads that are worthwhile/interesting, the less good it is if we are cornered into banning them and meaning we pretty much can't ban any long-term users.
So we tend to ban:
1. If it's the 'Russian Troll', who caused this ridiculous rule to be in place
2. If we spot a new user trolling early enough or an old troll posting early enough (often what has happened with MPBH's many many new accounts)
3. Occasionally if MPBH takes it to the limits of xenophobia we decide that it's worth fucking up a bunch of threads just to be briefly rid of his horrendous personality.
4. If we decide there's just no other way.