If I'm not mistaken, the intersection of where n and n^2 cross has no bearing on the significance of that 0.5 point on the X axis on the n^2/(n+1) curve.

Recall that these are graphs of the derivatives, not the curves themselves. The point you've marked there is roughly where the derivative of n^2/(n+1) would have a linear tangent. In other words, it's where the second derivative of n^2/(n+1) roughly equals to 1, which has no real relevance that I can see.

I agree with Smooth that the proposed n^2/(n+1) curve just as a superlinear head and approximates to linear. The effects are to ward off profitable micro voting which happens already, but would likely increase in an otherwise new working economic scheme (higher curation, some free downvotes) because other avenues of abuse would be more noticeable and thus less profitable.

Ideally, I'd probably prefer just a 'spam tax' of say 30-50% up until Steem value is around 1, and then completely normal linear after that. But if that can't be implemented, then I'm ok with whatever convergent linear approximation curve.