The more I think about this, the more I like the idea. It seems like it would help to make things more equal. However, if flagging is still an option in this scenario, then it's function needs to be redefined. Instead of what it does now, perhaps it should be that red emergency handle on the city bus that no one pulls unless it's an emergency. Such as in the event when plagiarism is discovered, or when someone is being abusing to another user. Perhaps the flag could disallow the post author from posting anything for, say, 24-48 hours.
The problem I see with this, however, is human nature. If there are 2 options, then when someone's emotions take over they're going to choose the stronger weapon of the two.
This conversation always comes back to having a person or small group of people to act as the referee and make the call. In the case of the flag - if it were defined as I've mentioned above - when one tries to use it, perhaps it could be forwarded to a moderator of sorts to make an objective call based on reasonable guidelines. If the mod can tell it's retaliatory, for example, don't grant the flag.
We always say that anyone can use the flag however they see fit - but if your idea becomes implemented, then that ideology would shift to the dissenting comment, and I feel the flag would be something that requires approval.