WIth millions or billions of posts (and therefore millions and billions of users voting all the time) , the self upvoter wouldn't be able to have a significant impact on reward pool distribution, even with a linear model.. there would be too many other votes being cast.

With billions of users, assuming the whale population increased at the same rate as the rest of the population, i don't think even a whale of comparable size to the ones we have now would be able to make much of a difference by himself.