Kind of late reply but it already exists in the Opening Explorer.
For example, I just followed a game line and chose the following game:
http://www.chess.com/games/view?id=4419154
I can comment on that game if I want to. The downside is you have to be a premium member (diamond or platinum) to fully use the Game Explorer. Not sure how limited you are as a basic member or if there is another way to access specific games.
Can you provide this type of database where members of chess.com commented on famous chess games.