It's been brought to my attention today that suddenly Blogger isn't allowing comments from outside Goggle or Blogger accounts. I don't know why! I've got the thing set up to "allow anyone," honest.
Hopefully it's just a temporary Blogger hiccup, but if'n you're having trouble posting comments, you can always try the "anonymous" option. It will let you use a name or not. (sigh) Technology, eh?