i agree the post experiment econ was the best, although it wasn't ideal either, as this level of superlinear heavily rewarded collusive vote stacking on certain posts
it was also expensive for abit and smooth running the experiment
i believe with something like n^1.2 or 1.3 up until a certain point, and then linear from there, we could enjoy pretty much all the advantages of n^2 with very little of the disadvantages
in addition, i think a non trivial amount of free downvotes is a must (although 100% is far too much, i think 25% of upvotes is more than sufficient)
increasing curation will further close the gap between voting for legitimately good posts from others and just directly shoving the vote rewards back into your own pocket (which would be much harder with slight superlinear and some free downvotes)