I had toyed with the idea of bringing up a unification of the mailing list with discourse, but wanted to wait for some more experience of LLVM having undergone just such a move (including the import of historic mailing list posts). It’s still a bit early to tell, but my impression is that it’s a substantial improvement and worth the hassle.
While I’m not a regular on the cpython repo, I’m quite active in other ways in the broader ecosystem, and I much prefer Discourse as well. I find the mailing list hard to navigate, new messages are hard to find in longer threads, (if you’re not already subscribed to all of python-dev), quotes are frequently broken/unreadable, etc.
Discourse isn’t perfect, but having the option to set notifications (e.g. each comment delivered per email) per topic or category is a huge improvement, to say nothing of the much better UI (e.g. quotes, search, reactions, etc.)