Restrict viewing of Comments to only certain groups

We have a web site that is open to the public but we also have registered members. We restrict the ability to post comments against articles to registered members. We would also like the ability to restrict the viewing of comments registered members or particular joomla groups.

It would also be useful to be able to specify restriction of comment view to particular categories.

I am not sure if we are alone in this requirement.
Does anyone else have this requirement?

David