Screening links wouldn't help, not without a sophisticated URL catcher and that just harms the end-user because it'd be us humans that would have to put up with it.
The bad thing about deterring bots is that the only real effective ways to do so also put off new users or make the human experience more annoying, and it's ultimately pointless as bots get updated and then they have new ways to bypass whatever you've got to deter them. It's an ongoing arms race, humans versus machines. I saw the Terminator, I know how these things end. I think it's better to put up with the bots every now and then rather than have all new members screened by machine-sniffing dogs.
Just report the bots and let the staff deal with them.
