I’m still working out the kinks in the commenting on the new blog software. For now, you should be able to leave a comment like before: anonymously, with your info., or by registering and logging in.
If you had a login on the old blog software, it didn’t get transfered so you can use the link at the top right to register a new account if you’d like. The benefit of registering is that you can subscribe to comments.
If you are an RSS person then you can subscribe to the comments feed for a post or for all comments. If you are on an article page and subscribe you should also get the option to subscribe to the Comments RSS for that article.