Yes, I have engaged with Konrad before on this issue on twitter and GitHub. However, I have to say I disagree with most of his take on backwards compatibility issues. I don't want to revamp that discussion once again but I don't buy this "old code" argument. Old code also has to be maintained continuously. I don't mean to break things in every release but then again any "ENH" PR can be rejected with the same argument such that we can only fix bugs and nothing else.
Personally, this was the reason that pushed me away from matlab with strange syntax and unusable UX choices that has been around since 30 years (8.3 filenames, nargin, nargout frenzy etc.). But even mathworks break code pretty often in every toolbox, see some of the exclamation marks, say in,
https://ww2.mathworks.cn/help/control/release-notes.htmlThese keywords won't be removed, possibly, until v.1.5.x only warning will be emitted hence there is ample time to adapt. To be clear on the Python3 detail, it was about the keyword order restrictions.