I will try to make it simple. With the exception of disagreement on rewards all down votes apply to the author. They have full control over what they post. What they have no control over is the amount of rewards that are voted for on their post.
Simple Idea. A post on day 7 would have received 100 on rewards. 50% going to the author and 50% to the curators. Authors share would have been 50. The post get down voted for 30. In the system I propose the curators at the top would lose curation rewards. Lets pretend the top three curators all voted at 10. They would receive no rewards and be eligible for no rewards from that post. The remaining curators would still receive a curation reward based on 20 since that is what is left.
The Author then receives the 50 reward points that prior to down votes being calculated they would have received, the 30 points removed go to the null account.
The reason the people can up vote the post after a down vote does nothing to discourage I don't like it, you, or the concept behind the post, in other words people that use the down vote as a retaliatory tool. If an automatic comment is made under the down voters name then the people can decide if the down vote was really warranted. This would probably not be able to be coded, but the people that already voted or down voted on the post would not be able to down vote the down voter, the amount of down votes received would then be added back into the post allowing the curators to receive a little bit more of a reward. It would have no effect on the Authors share of the reward as it was untouched. The down votes in excess of the original down vote would go to the null account.