"You cannot make a post so soon after your last"
Right now you have to wait a while between each post, which is really irritating if you're a fast typer. Or if you just snorted a line and are going to ham on every topic with logical fact based replies.
The forums have a thing so newbies can't post without admin approval, surely that filters out the spam bots? So how about reducing that time from whatever it is now to 30 seconds or something? Long enough to stop a script DoSing the place with posts, short enough to be usable.