The 5 minute rule might be better. But content is king. And the 50/50 rule won't encourage better content imo. There is an important benefit to the 30 minute window you didn't mention, which is it's more profitable to vote for an underdog than it is to vote for an already popular author. That incentivises people to join, because anybody can be a winner.

If you do change the ratio to 50/50, I would argue that the time for curation donation be INCREASED rather than decreased, to increase the incentive of finding hidden gems and DECREASE the incentive of voting the same authors all the time.

Neither solutions make self voting less profitable than good curation. The only way to make it more profitable to curate, would be if there were the potential to lose voting rights. The downvote is the negative of the upvote and serves a purpose. The problem is people use it more often as an emotional reaction and so when most people get one they take it personally. When it comes to delegation, we're talking about people renting stake, which means they don't actually have the incentive to grow the platform and they can be selfish without risking capital losses. To prevent that you need a counter for delegation, and that is vote negation. Another negative like the downvote except instead of downvoting an author, you would be downvoting the curator and the author would never see a difference in payout.

2 stakeholders, one with 100k SP the other with 80k SP. One doesn't like the way the other votes so he negates their SP. So the first whale is left with 20k SP to vote with and the second only has the power to power down, or negotiate what behaviour needs to stop to get their voting permissions back.

It was suggested this would be "abused" when the code was written, but the cost is a lot more than the downvote which is already heavily abused by emotion.