I think you should be able to delete comments on games and forum threads. Don't you think so? Like, if there are too many spammers on your game, just delete 'em! Or, if there is a total noob on the forums, delete 'em! See what I mean?
No, removing negative commentary means that all games have a 100% approval rating.
That's not a good thing, you effectively might as well remove comments. It'd be faster, easier and would probably create less long term effects.