Comment by duskwuff

I have a feeling it might be less "avoid negative publicity"; more "give a premium experience to influencers" (for a broad definition of that term).

A user - like mbo's mother - who posts a lot of content which generates a lot of reposts and other positive interactions is basically a gold mine for Facebook. It's in their interest to treat that user with kid gloves to get them to keep posting, even if it means foregoing some revenue opportunities.