Non linear voting model means not proportional.
While I prefer meritocracy over democracy, quadratic reward curve will favor preminers and the rich even more than the current linear reward curve.
No wrong in rewarding stakeholders, but if it is so good, why are dividends of corporations not distributed this way?
10 accounts of 100SP will count 1/10 as much as 1 account of 1000SP.
It will encourage collectivist workarounds such as currie, MSP and other menaces.
This way, proportionality/linearity will be achievable, because even the bigger users in such an aggregation will still be able to gain from their participation.
Even if x>y then (x+y)^2/x^2=1+2*y/x+y^2/x^2, and the gain is positive.
What is your opinion about such collectives?
Since you mentioned moderation, you should be enthusiastic about them.
MSP and currie have moderation.