Most people know how much their vote is worth, If an individual wants to reward a chart with a $200.00 vote reward they know they did that. The chart poster may be in cahoots with the reward giver or not, it does not matter, it was the vote giver that provided the excessive reward. The poster did not ask for it.
No there are no incentives for bot sellers to change at all, I do not see the downvote pool changing that either.
And yes the re-poster should decline the rewards in some cases, but that is not going to happen, it has not happened on twitter, on youtube on any other social media site, while the poster may not be receiving rewards the advertisers on those sites do receive rewards,(such as steemits ad revenue), and the site owners receive rewards. In many cases the click to share links come with no exceptions. When you go to Wikipedia, their click to share images come with all the source and copyright info, so it is possible for other sites to do the same if they choose to when allowing/requesting people to share their content.
But the downvote pool system I think is a done thing and steem and the witnesses do not need my approval to make the changes. It is just another HF20 RC's are gonna set the people free campaign.
There is incentive from the buyer though and many of the bits biggest customers are likely to get flagged.