Nobody complimented me on getting (a) (b) (с) into my post, so I'll just repeat it here.
Feel free to copy and paste the (с) into your own posts (of course it's © Brian Chandler 2009), and the malevolent may insert just the 'с' into 'f***' or whatever. So the "filtering" crap messes up genuine posts, and doesn't stop evil ones. I think it's time for it to go.
The sequence left-round-bracket : lowercase c : right-round-bracket should not naturally occur in a PHP program, so it should be easy to find.