We'll create fresh WordPress site with cbnet Multi Author Comment Notification installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Easily enable email notification of new comments to users other than the post author.
Via Dashboard -> Settings -> Discussion, enable email notification to users by site admin, user role (Administrator, Editor, Author, Contributor, Subscriber ), or define arbitary email addresses to notify. Also, optionally disable email notification for comments left by registered users.
Email notification for individual users can be enabled via each user’s profile.