Neither Safari, Chrome/Chromium, IE, old Edge, nor new Edge have substantial HTML and CSS developer documentation on their own web sites. Their vendors - excepting Apple and the WebKit contributors - all chose to work with Mozilla instead to put their docs on MDN: https://blogs.windows.com/msedgedev/2017/10/18/documenting-w...

It seems to me that as far as the browser makers are concerned, MDN is as close to authoritative as you can get without going to the standards documents themselves - and the standards don't give you browser compatibility matrices or make any note of browser-specific quirks.

MDN may be a wiki, but it certainly isn't treated like one by the people who are most interested in it being accurate and up to date.