Hrm ... I have this idea, based on a flash game MPORG I play. Basically, before you can use the /chat function in that game, you have to play this little "literacy test", where you prove that you can differentiate "you're" and "your" and things like that.
I don't know how easy it would be for Mitch to implement, but how about something like this: After you agree to follow the rules, the new user has post access to High School chemistry, and Citizen chemist only. Maybe, even before that access is granted, there's a little CAPTCHA-like quiz, reminding them to write grammatically correct English and not, "i wuz hopng for help, plzzzzzzzzzzzzzzzzzzzz"
If they want access to Undergraduate Chemistry, then an answer to a chemical trivia question is needed, something like the formula for water. Access to the Organic Chemistry boards might have a question like what is the generic formula for an ether, with multiple choice options like R-O-R' and R-O-H. If you can't get it right, you're told so, and hopefully the user realizes they have to try a little bit, or sod off if they think it's too much work.
If you want access to Analytical Chemistry for professionals, you'd better be able to answer a question like, "Etching a copper PC board with ferric chloride is an example of: red-ox reaction or decomposition?" Or you simply get told, to try again, when you're ready.