Déjà vu. Previously (checks email …almost exactly 5 years ago?! Christ, it was a long time ago), the web powers that be announced they were going to collaborate on a new web docs wiki.[0] I don't think it went anywhere because, well, MDN already existed.
I'm glad they finally just surrendered to MDN, even if it was many years late.
They chose a different license that made it more difficult than it should have been to integrate content from MDN. The two sites' backends were completely different, too, so the source texts needed to be tweaked before publishing. I also remember that for for many of the docs, they favored basing them off MS's contribution (IIRC). It also had a very un-wiki-like atmosphere, where the lifecycle of a change resembled a code review, i.e., the opposite of the "be bold" policy that led to the success of Wikipedia (and the early days of developer.mozilla.org).
"One of our guiding principles in developing Microsoft Edge is that end users should never have to worry about which sites work in which browsers. This philosophy—”the Web should just work for everyone“—led to our choice to target the “interoperable intersection” of web APIs in our browser engineering."
Many sites already don't work correctly in Edge, IE11 nor Firefox - it's too late, these are minor browsers, used by a smaller fraction of end users. End users on on smartphones use 95% a WebKit originated based browser aka Chrome/Safari. Chrome and Safari are bigger than the rest on desktop.
Sites in 2017 are tested against Chrome and Safari by web developers.
Minor is very relative here, especially with regards to Firefox.
IMO anyone who only tests against Chrome and Safari is seriously wrong. The amount of features not supported by Firefox or Edge are relatively small and so basically everything except for a few special cases should just work everywhere.
It depends on the user base. Customers of the company I work for mostly use IE or Edge and only Chrome because we highly suggest it. Without decent IE/Edge support we would have less customers.
I'm glad they finally just surrendered to MDN, even if it was many years late.
[0] https://www.w3.org/2012/10/webplatform.html.en