You won't ever be able to stop 100% of all spam, wihtout blocking legitimate posts! So, maybe you can find a way to add a "Report Spam" link. I am not sure where Spam is a problem on your site, it isn't really an issue from my perspective, but if it is in new posts, maybe adding a report spam button on every new post would help.

My bigger concern is that my email gets farmed from sites very often, and I get hundreds of spam emails daily. It seems the more that sites require you to register, the more this is an issue. I have no idea whether anyone has farmed SSC for emails or not, but that would be something to try to prevent if you can.