Nice but not the best solution. Not only the filtering method, but mostly the language used. A php post-data filter would be more efficient. And don't forget, as the system gets better, users are getting better as well. And they will invent spams like "s3lling C V V ch34p". Try filtering that. But once again, nice job.
Unfortunately I don't have access to the server xD
Thats why I wrote a client side script to deal with that while waiting for adum to hopefully implementing some spam protection...
It's hard to use a javascript, adding it manually. A firefox extension would do it, I heard there are JavaScript XUL converters, so it shouldn't be that much hard of a job. I can't say it for sure, I never used XUL before nor wrote firefox extensions.