[If you're reading this on Facebook, don't worry this is for people who comment directly on the blog.]
I've had to turn off Anonymous commenting as the sheer volume of spam has trained gmail that all comment notifications from the blog are spam and then I miss real comments. 99% of the spam is from anonymous users so I've restricted comments to users who are signed in and we'll see how that goes.
If you have a google account or any other valid OpenID account you can comment. You may not know you have an OpenID, but you probably do. See: Surprise! You may already have an OpenID.