Ah cool, thanks so much!

I'm not sure how customizable Trac is, but one idea would be to implement reCAPTCHA for anything marked as spam (assuming robots are causing spam issues and not users). If it gets solved, it's probably a human entering something on the other end.

This is a Python 2 reCAPTCHA module I forked/updated: https://github.com/dave-gallagher/recaptcha-client-1.0.6-ssl