"You do realize that ideology is not cleanly divided between two political parties, and that neither party has a consistent ideology over time or at any given time?"
Yes, I do.
"neither is right or wrong about anything."
Actually, it's quite common for both to be right (robbery should be a crime), for either one to be right and the other wrong (starting a war with Iran would be bad no matter what Republicans think; trade protectionism is not good for our economy no matter what Democrats think), and for both to be wrong (infinite copyright is not good for creativity).
"That is further true with Supreme Court justices, who have no reason to have any party affiliation, generally have none, and are far more nuanced, consistent, and reasonable than any political party."
That is what I'd like to see, but recent history proves the exact opposite. Supreme Court justices align themselves with a party and pretty much follow it slavishly even contrary to their own declared ideology and rational conclusions. Maybe Justice Thomas is less partisan than most, but they're all far more partisan than ideological or rational.
That's why I explicitly said Republican and Democrat and not left and right or conservative and reactionary.
Lucky for us, most cases are still technical and detail rich rather than battles over federalism, abortion, and other hot button partisan issues. Our only remaining shred of non-partisanship on the court is that many issues don't yet have a partisan aspect.
"It's sad to see the sort of Fox News / MSNBC style partisanship you represent on Hacker News, where what you disagree with is called "Democratic" and what you agree with is called "Republican.""
It's the only realistic view of the present court and its appointment process, no matter how sad it is for the country.
Also, what I disagree with is seldom called 'Democratic'; I'm a registered Democrat. It just so happens that partisan Republican motivated reasoning was better and more valid on the single case under discussion. Since I'm not trying to get appointed to the Supreme Court, I can afford to admit that.