I hadn't realised that Blogger had an automatic spam filter for comments. It puts them in a little folder. When I checked, there were non-spam comments in there but no spam ones. So it doesn't work very well.
Those comments have now been released onto the blog. Sorry about that. Now I know where it is, I'll check in there more often.
I have moderation on for older posts, which I am not too efficient at monitoring either. So some comments have been released into the wild from there too.
One day I'll get the hang of this.