Well, technically, in an open environment as HubPages, still should not be able to be done. Who follows your work isn't up to you? You don't get to decide, who can and who can't. That is the basis for discrimination and why should it matter? You don't have to approve the comment to begin with, so it's irrelevant. If that person doesn't like the fact that you don't accept their comments, then they will delete themselves. 