Half Sigma has been subject to a huge amount of comment spam during the last two days, so I turned on the Typekey authentication requirement. Sorry. I would rather people didn't have to sign in in order to leave a comment, but unfortunately for every legitimate comment I was deleting ten spam comments.
UPDATE: I turned authentication OFF now becaue I was unable to leave a comment on my own blog when it was turned on. I'll probably get spammed again now.