It would be nice where if a new poster is placed in moderation que and once approved they get an email indicating such. That way you bring your users back.
As it stands now, when uses have their post's placed in moderation que they don't know whether their post/s were approved or not. So perhaps an option in the ACP to allow an email to be sent whether moderated posts are approved or not would be appropriate. Also, an email can be sent if the post is denied with that option selectable in the ACP.