"I don't think this should be done by default as it will break people's expectations and, perhaps worse, compatibility."
I won't mind another thread naming API, if somebody does this. :)
But personally I expected python to name my threads (and if the OS supports it, on that level), I was actually surprised to see that it doesn't, mostly because I remembered a patch for FreeBSD, which did this years ago, so I thought it has been merged into mainline since then.