++, but..

"I think there are better ways of dealing with it. One might be to have the "Create" button changed to "Post anonymously" when not logged in, which I would expect to be enough"

I just tested this by attempting to reply to your post via the .com domain, rather than the .org to which I'm currently logged in. It shows:

You aren't logged in.

Login, Create a new user, or hit "Create" to proceed in posting your node.

And I had to scroll down to see the post and it's associated buttons. Perhaps you're right in so much that there's some more HTML/CSS fu which could be used to make this seem more obvious, though people may still miss it, for example browsing using a text based browser. On a related subject. I use the (poll winning;) Perlmonks blue theme. The site looks a lot different before I log in, so it's much less likely (if not impossible) for me to think I'm logged in when I'm not. I don't think the site has ever logged me out in all the years I posted.