The problem with curation being at the discretion of the author is that it creates a race to the bottom. Some (large) voters will let it be known that they will only upvote posts with high curation rewards for themselves. Or naturally, posts with higher curation offered will do well. Which forces authors to compete for attention by offering higher and higher curation until they all (or many) are reaching the maximum curation possible. Which means voters who want to give 100% of their vote to the author, or 75% will not be able to.

Well said. I stand corrected ;) You make a good case for a much better solution, which 50/50 was a poor one to try which I disagreed with.