> Maintaining Python is already expensive [...] There are already enough bugs waiting for you to be fixed ;-)

BTW I basically agree with this. I think this is not a high-priority issue, and I have my eye on some of those bugs. :-)

I think the fact that it's per-*language* (despite my inaccurate phrasing in the OP), not per-locale, simplifies it some -- for example the whole `.UTF-8` vs `.utf8` thing doesn't appear. And in particular I think if/when someone decides to sit down and make an implementation of this, then if they take the time to carefully read and absorb the relevant pages of the standard... this is a feature where it's pretty feasible for the implementation to be a self-contained and relatively stable and low-bugs piece of code.

And in general I think even if nobody implements it soon, it's useful to have an issue that can be pointed to for this feature, and especially so if the discussion clearly lays out what the feature involves and what different people's views are on the API. For example #18236 has been open for 6 years, but the discussion there was extremely helpful for me to understand it and work up a fix, after just being pointed to it by someone who'd searched the tracker on seeing me send in the doc fix GH-15019.