i dont think notifications are neccesary, however i do think email notifications are a usefull tool, expecially for me cause i dont check my page that often unless im wondering what my AP is
We will have some sort of way to mark that you approve of a comment, the semantics of calling it a "like" button or a "thumbs up" or a "karma score" or whatever will be determined later.
Maybe you won't get points for liking something, but the person whose comment you like will get some karma points or something. It's still being worked on.