I wanted to comment positively on Mo's blog today. I signed up and received a confirmation email, but was unable to log in. I then tried to comment anonymously, and my comment was not accepted. I've sent an email to the people who manage the signin / sign up, tho obviously they won't reply in the middle of the night. But I think something's wrong when it invites you to comment anonymously and then won't let you 
PS. Problem solved. Instead of forgetting my head, I forgot my name!