As a matter of fact, self votes by whales have a much smaller effect.
To believe that I needed an example. If the curve starts flat, of course also whales should profit less when upvoting an own article on which nobody else has voted so far.
The real culprit is the vote regen change from 40 > 10. That means a possible 100% self vote is 4x as powerful as before.
Yes, I mentioned this in my linked article, too. It makes self-votes much more lucrative than before - together with the linear reward curve.
Addition: I also think the former idea to have only four fully rewarded articles per day was reasonable as it made it less attractive to make many short low quality posts per day just to upvote them oneself.
I was comparing linear to the quadratic curve we had before. I see now that you meant sigmoid. Rewards are calculated by total Rshares contributed. Depending on the exact implementation, a megawhale might just get to the peak all by themselves with a sigmoid curve. Don't underestimate the disparity between whales and minnows - it's enormous. Anyway, it's not possible to talk about details like that without knowing the exact implementation.
I have to say this sigmoid function is 'fascinating' me as it could avoid the disadvantages of the linear and the quadratic curve. Therefore I wanted to attract some attention for this idea and see if some other steemians might be interested, too. :)
Of course the exact implementation is what finally would matter, but before to rack my brain too much, I wanted to plumb if the idea is able to attract some interest.
Anyway: thanks for drawing the attention on diminishing returns again!