GameFAQs does this. I dunno, like maybe have it appear in your inbox or something? So basically the current quote notification system, except apply it to posts.

Is subscribing to a thread not scratching the itch for you? You get a single email if a thread is updated, with no additional emails until you visit the thread in question 

 

I will admit to having never used this feature before. I always wondered what it did. >_>