Redirecting with mod_rewrite without breaking OpenID

On philihp.com, I redirect the root address philihp.com to philihp.com/blog. I do this with mod_rewrite, since it’s much faster to do an HTTP Location header based redirect than to use an HTML meta tag redirect. I encountered a problem with this, though. I want to be able to authenticate with the identifier “philihp.com”. Not “openid.philihp.com”, [...]