Comment Moderation Bug?

Okay, so I’m testing my snazy new blog. I post a comment without logging in.

Name: anonymous
Email: [email protected]

Then I administer the site. I go to the moderation tab under manage and approve the comment.

So far, so good.

But then I post another comment by anonymous with the same email address and IT GETS APPROVED WITHOUT MODERATION!

Can anyone help me out? Or is this a known bug?

The problem persists even I revert to the Default Theme, so I don’t think I screwed up my comments.php file.

thanks,
Roman