On reddit, before they fucked the api, you could use third party tools to identify and tag users that were known trolls, and even have a good chance of identifying ban evaders.
Automod could filter out a lot of trolls and assholes just by fifteen minutes of typing, so users never had to see the worst stuff, even when the trolls weren’t identified.
Blocking after the jerks jerk is a slow whack-a-mole process