I've recently seen that it worked pretty well, so I might as well suggest it.
How about we were only allowed one review/comment on each game? I've seen people who have repeatedly commented on one game over and over again to gain the AP.
This would also work very well with an edit option just in case the person makes a mistake.
Profile, games, and the news share the same system. So if you make it so it's only once comment it will mess with the news comments and profile comments. To avoid this problem you'll have to separate the game comments from other comments, which is even more work.
This is a bad idea. Most people don't even post more than one comment per game anyway.