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.
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.