Adding Node Reference to a Comment
You could achieve this with Comment Notify module.
We use it on few sites and it works great out of the box. 

From module page: 


  Features
  
  Mail registered and anonymous users about comment follow-ups
  
  Allow users to unsubscribe from notifications on a specific post with
  a single click
  
  Allow registered users to preset their follow-up setting in their
  profile
  
  Users can choose to get notifications about all comments on a node or
  just replies to their comment
  Registered authors can get notifications about comments on their nodes
  Note: Since it only notifies you about published comments, this is not a solution to notify admins when they need to moderate comments on their site