Decentralized social RSS feed / article recommendations could totally happen if the community came up with a standard way to implement it.

Re-posting / paraphrasing a comment I made in a discussion about decentralized recommendation algorithms for RSS feed content:

People used to post a "blogroll" (and sometimes an OPML file) to their personal blogs showing the feeds they followed. That was one way to do decentralized recommendations, albeit manually since there was no well-known URL convention for publishing OPML files. If there was a well-known URL convention for publishing OPML files a client could build a recommendation graph.

OMPL files in well-known locations would be neat but would only provide feed-level recommendation. Article-level recommendation would be cooler.

One of the various federated/decentralized/whatever-Bluesky-is "modern" re-implementations of Twitter/NNTP could be used to drive article-level recommendations. My feed reader could emit machine-readable recommendation posts based on ratings I give while browsing articles. My feed reader could consume these recommendations from others, and then lots of fun could be had weighting recommendations based on social graph, algorithmic summary of the article body, trustworthiness of the poster, friend-of-friend status, etc.

I thought about some of this stuff back in '05 when I tried to contribute to ttrss. The maintainer didn't have much interest so I dropped it. I've thought about it periodically but never had the initiative to do anything with it.