To bring this thread back to encouraging diversity, I must point out that diverse English dialects are not all there is to diversity, folks.
Nathaniel Smith writes:
In particular, it emphasizes that the new text is accomplishing "the same goal", "maintaining the original intent",
That displays a great misunderstanding of that goal and intent in my opinion. The original intent clearly includes providing *concrete* guidelines, because no student of Strunk & White would use a reference to Strunk & White if the phrase "clear and easily understood" would do.
Strunk & White is not a grammar of "Standard" English. It is a Zen- of-Python-like collection of precepts, many of which inform my own writing in Japanese (!!) as well as in English, and my Japanese and Chinese students have expressed appreciation for them. While the quirkiness of Strunk & White appeals to me personally, replacing it with an explicit set of guidelines directly modeled on the Zen or an alternative reference would serve the purpose as well.
But I do not know of a good substitute for this purpose. I don't think David's suggestion of Zinsser would serve so well. It is a textbook and quite discursive, while the table of contents of Strunk & White is quite Zen-like, and little more than twice as long as the Zen.
From the lack of any mention of this aspect of Strunk & White, it's clear that the commit was made with little or no consideration for the many developers, current and potential, whose native language is *not* English, nor for some neuro-atypical programmers, for whom generalities like "be clear" may be deterring and explicit rules comforting. That doesn't mean simple removal of that reference was the wrong thing to do, but it does mean that removing it without replacement needs more justification than "it's a 'relic of white supremacy'".
I agree that the goal of encouraging diversity among community members justifies substantial cost, which is repaid in many ways. It is certainly true that some of the precepts of Strunk & White are simple grammar rules that are specific to Standard English, and in that sense center whiteness. But the loss to some, perhaps many, developers from failing to provide *any* concrete guidelines may be large. That should have been considered before committing, and in my opinion, replacement guidelines or an alternative reference included. This loss was mentioned several times in the discussion on Python Ideas -- and ignored.
I sure hope it will be considered now.
Footnotes:  And probably suffers from "centering whiteness," though perhaps not to the degree that Strunk & White does. It's been a while since I've looked at Zinsser.