Comment by SXX

If your project is popular enough to the point where tailored automation make sense there no way to fight spam really.

If its small enough you can usually avoid all the spam bots by adding any none-standard flow in registration procedure. E.g static picture or audio of something only your audience know with like drop down option to click on picture saying "I'm not a bot". Or add one more email verification for first post or edits. Or make users watch large YouTube video at certain timespamt with correct answer, etc. Anything non-standard works.

Breaks 99.9% of automation and SERP spammers wont bother create unique one for your wiki / forum / etc.

If your site is very popular you're fckd obviously and it's just arm race. This is where you can use Hashcash or something that will burn lots of CPU / GPU / RAM / etc single time so spammers will just blacklist you.