Is there any way to prevent these bots?

[Qwertygiy]

They don't post on the forums, they merely comment on just about EVERYONE's user profile with random junk about profiles, pictures, and an email address -- usually it's obviously an attempt at ODing.

Is there a way to "complexify" the commenting system a tiny bit so that whatever program[s] finds the text box / submit page can't find it anymore? Hopefully something "invisible" to players, because I don't think it would be worth it to throw in a CAPTCHA.

[Jacob__mybb_import1]

The registration form already has a CAPTCHA, a security question and anti-bot JavaScript, so either the bots are really advanced, using a CAPTCHA outsourcing service, or they're not bots at all, but people being paid minimum wage to write spam posts.

Can you link to some of the comments? I might be able to code some sort of spam blocker based on the keywords.

[Qwertygiy]

I already deleted all of them via the admin page.

It's definitely not a person simply copy/pasting, it's about 1000 profiles at exactly the same moment.

I do know that they all include an email address when they do it, and I can't think of any other time someone would use the @ symbol in a comment. Maybe you could do something about that.

[Jacob__mybb_import1]

Comments with email addresses are now blocked.