On the 'valid urls' issue.
I just had this crop up today twice.. No way you can force everyone to use valid urls, you can get complete destruction inside threads (they are rendered completely unreadable with php errors and duplicate header errors) rendering a thread unusable by anyone after them. It definately can be a security issue since any user can register and create a hassle in threads. I've turned off that one section for now and I'm hoping there will be a workaround for those who post http:slashslashhttp:slashslash in their posts back to back (on purpose or by accident).