When posting a post with a script html tag (only*), it appears as empty and there is simply no content:
Yes, html isn’t rendered in replies, you also can’t execute client side scripts within topics in this manner. Both are known.
Is there really no way to check what it renders to and prohibit such posts? 
alright, so I guess if it is a wontfix then I would have to warn/ban users and delete such posts?