If the user is a Contributor in WordPRess, this mostly happens by default.
You are the site admin - you'll get moderation notices for comments on all posts.
Your guest author, as the author of the post, will get notified there are comments on their post.
These forums were CLOSED to new posts on November 19th, 2012. New forums are here: http://www.studiopress.com/forums/
and you will need to SIGN UP AGAIN.
If you need assitance with setting up your theme, go to http://my.studiopress.com/
and read the SETUP links or the TUTORIALS link on the side tab.
If you need Account Assistance
, file a help desk ticket at the same location.