I think the system needs a little tweaking. An author has no ability to decide who votes on their post unless they are buying up votes. The removal of rewards for over-valuation on a post is nothing the Author can do about, the Author is not the guilty party, the person that issued such a large reward is.
Down voting a post to $0.00 is I feel wrong in the case of what people see as over rewarded post and to track back for the entire 7 day period of post and zero them out is also very wrong and has nothing to do with a post being over valued.
If I see plagiarism I will down vote it, that is pretty much it. That is the authors fault and he deserves to have his reputation destroyed and all profits removed from all post past, present and future.
If a post is over rewarded, and the down vote is all about returning rewards to the reward pool, then go to the person that over rewarded the post pick one of their post to down vote, and state in the comments your post was down voted because I feel you over rewarded this post. Rewards removed and returned to the reward pool, person that was over rewarded gets a temporary rep and hive boost, and the offending over rewarder gets some of his reputation hurt and his pocket book hurt with out hurting the Original Author, and the original curators of the post.
Abusive down voting is and does happen to often on Hive. Perhaps people can come together and lobby for a new down vote system that can be implemented in HF 27.