[WIP] bpo-40533: Make PyObject.ob_refcnt atomic in subinterpreters by vstinner · Pull Request #19958 · python/cpython

Perhaps this is somewhat emphasized by the "experimental" part, but could we possibly make it a bit more crystal clear that this is only a temporary stopgap measure? I personally find that "until subinterpreters stop sharing Python objects" could be interpreted as a near indefinite amount of time; I'm not confident that most readers will go over the full context in the bpo issue and related discussions.

Normally, this wouldn't be a huge concern, but I think object.h is likely one of the most public-facing header files in CPython, so it seems important to communicate this as clearly as possible.