I'll take a stab at the "let it be natural" question:
It means not placing content customers don't want in equal or more prominent positions than content that is important to them. I don't want highlighted ads inline, pushing content that I want to see down off the page (and exacerbating the naive solution you mention of displaying things in chronological order).
This is not to say that I don't agree with your correct insight on the technical difficulties, but want to add that I think part of the problem of the problem of "natural" is not just the complicated algorithm of showing relevant information, it is the fact that Facebook is prioritizing things customers don't want in that algorithm.
It means not placing content customers don't want in equal or more prominent positions than content that is important to them. I don't want highlighted ads inline, pushing content that I want to see down off the page (and exacerbating the naive solution you mention of displaying things in chronological order).
This is not to say that I don't agree with your correct insight on the technical difficulties, but want to add that I think part of the problem of the problem of "natural" is not just the complicated algorithm of showing relevant information, it is the fact that Facebook is prioritizing things customers don't want in that algorithm.