Sorry, for those of you who have a TypeKey account, I didn’t add the code to actually allow you to sign in using your Typekey registration and leave comments. Ooops. Hopefully it’s working now!
OK, so it isn’t working. The Typekey site tells me that this site hasn’t turned the feature on, when, obviously, I have. Ugh!
Now it works. A case of really bad documentation on the TypeKey site, explained here.