This is a big step forward, and is also making me nostalgic for the Friend-of-a-Friend (FOAF)[0] blogrolls of the early 00’s. RDF-in-HTML standard that could express recommendations and relationships.
That said, I’m glad to see Webmention adoption. It’s got a much clearer purpose than FOAF (it might’ve been a little too expressive) and fits nicely into the current web ecosystem.