in practice, it seems like when they're adopted by states, the states just try to balance things 50/50. that might be good, but it's not non-partisan, it's just the partisan sides agreeing to horse trade.

we saw that with the old north carolina map. the "non-partisan" commission that drew the map arrived at a 7-7 congressional delegation, but to do that, they drew a map that literally had two districts bisecting the capital grounds in (deep blue, as all government strongholds are) raleigh - the line literally went between the capitol building and state office buildings on the other side of the street.

i don't know how you'd describe that, but it's clearly not non-partisan. there's no logically neutral system you'd come up with that would require drawing the border not just within the city, but directly through the heart of the city that happens to be the most blue in the state. the people drawing the map obviously knew what they were doing and obviously drew those districts to give the democrats two seats instead of one.