I think that you should be able to PM someone or at least have something that alerts them that someone new has commented on their profile. I also believe that you should be able to re-rate a game with no change in your armor points.
It's been stated before -- search for other threads similar to yours before posting.
Rerating just SCREAMS skewered ratings for games... one month a game would be 9/10, then a group of people who for some reason have a grudge against the creator, will rate it 1/10 -- thus resulting in a dramatic drop. You need to understand, many users on the website tend to abuse tools. Unfortunately, until they learn how to use them properly, there's no sense in bringing them back or creating them in the first place.
Besides, I understand you might slip your finger or something when rating, but that's just how it is. If anything, you should make sure to rate games properly (i.e. play them for 20 minutes to see if you like it, or something similar).
I think PMing would be nice, but it should be for NO AP. It isn't that necessary though as you can use email, instant messaging, etc. if you want to talk privately.
Re-rating even for no AP would be good because people's opinions can change, and even if there are some people who will abuse this system, there are already people who abuse the current system.