[nested]

I hadn't actually looked at the equation for curation rewards. I was under the impression that they were based on SP, but linearly so (and i missed the parenthetical statement to the contrary when i replied).

They are in practice somewhat superlinear because rewards are, and curation rewards are 25% of post rewards (ignoring reverse auction).

Simplified example would be someone with 1 million SP votes on an unvoted post and generates a $4 post value, so $1 in curation. If someone else with 100 000 SP votes on an unvoted post under the same reward pool conditions, that would generate a 0.04 post value, and 0.01 in curation.

In reality it isn't anywhere near this extreme, but the effect persists.

Because the extra concentration caused by superlinear vesting rewards to idle accounts like ben and dan (up until a couple weeks ago) would have to be counterbalanced.

Maybe, maybe not. In looking at incentives you have to consider that those accounts could become non-idle at any time and begin earning curation rewards and contributing to increased concentration (which as you point out has happened). So ensuring that even currently-idle accounts have a incentive to stay idle (and considering what would happen to concentration if they didn't under each alternative) is an important consideration.