I really have no explanation. I set the settings to X (i.e. it accepts X rated gravatars), my gravatar is rated G, and yet I get this:
Two gravatars are showing up; three are not. I've checked my own account and there's nothing wrong with my gravatar. I'd expect all or none to be showing up, not this. The theme I'm using is a child theme of mystique, and I'm also running the Spam Free WordPress plugin for comments (though disabling it doesn't fix the problem). Anyone seen anything like this?