That's where the curated annotation comes in. Elect someone (not it!) to be an editor, have others give pros and cons to the overall design philosophies in the intro. Have two relatively concise opinion pieces and be done with it. Don't have 5,000 comments on the fighter class going back and forth on why they're better or worse than 4E.Well that's a tangent sure. But why?
It's a MASSIVE benefit to have a properly annotated PHB - and it's a 5e PHB, so discussions of 4e shouldn't enter into the actual annotations. they might, but maybe a strict warning in the OP?
If you want to argue why 4E was awesome, you get your say. Someone else can explain why they disliked the design philosophy. Each side gets some arbitrary word limit. Ultimately I think it can be summarized in 3 words: "I liked it" versus "I did not". Same goes for things like halflings.
Anyway, do that, have a single person coordinate and then publish it to the DmsGuild as a free PDF. Just don't ever expect consensus.