I re-activated the comments system. WordPress has a feature to let you automatically disable the comments on any articles after a set period of time. Since most of my spam was coming on posts that I wrote a long time ago, it makes sense to set this up and allow comments again, because I have had some good ones in the past. I also should mention that you now need to sign up to the blog to comment. I guess it adds an extra hoop that a spammer would have to jump through to try to give them less incentive to waste their time and mine with needless comments.