In current WordPress, the only way for a comment to remain private is for it to stay in an “unapproved” status. It would be nice if comments could flow more easily between unapproved, private, and public.
When someone leaves a comment, an option is available to submit the comment as private so that only the post author will see it.
When a post author moderates a comment, an option is available to make it private.
A post author has the ability to privately reply to a public or private comment within the WordPress admin.
Jeremy, I really like the idea of private comments. I guess this is a part of the wider discussion around private posts.