here's my first official guess as well...

Rule 9: The text of the comic must include a written number, such as "Two" or "Eighteen".

I also suspect that there's a rule requiring either bad grammar or intentional mispelling, but I can't figure it out.

I was debating the ethics of that tactic, fpd. While I'm sure it would give valuable clues, I wasn't sure I'd have felt right doing it.

Still, I'm glad someone tried it.

You're on the right lines. What do the two groups you mentioned have in common? If you follow that commonality, what other groups would be banned?