I wanted to upvote an answer. I wasn't logged in. Clicked on "log in", got logged in automatically and then I was at the "Add OpenID" page. Seems like a minor bug as the site is not aware I am logged in.
We can't reproduce this.
It is possible if your browser is inappropriately caching the not-logged in page, which would mean you ARE logged in, but the HTML displayed is from a previous load.