Try requiring new accounts' first few posts to be manually approved. Then he'll have to make enough quality posts to build up credibility first. This is very di

Try requiring new accounts' first few posts to be manually approved. Then he'll have to make enough quality posts to build up credibility first. This is very difficult, especially for a script kiddie. Alternatively, you can take away the instant gratification by adding a cooldown of, say, three days for each created account. Then he'll have to register them in bulk and hope the humans don't spot the patterns. You could also try using Bayesian filtering, but you'd have to block the ASCII art first.