Restrict Comments by User or Role

Is there a way, or perhaps a plugin, that will allow me to specify which users can leave comments? All users must be registered to view the blog, but unless I missed a really obvious setting, even the Subscriber role provides comment permissions. I’d rather not deal with comment moderation, because I want certain users to be able to leave comments without waiting for an approval.

Essentially, I’m looking for something that can create a role (or specify a user) that provide true “read-only” access…without the ability to comment.

Any help is appreciated – thanks!