And as my view in that post foretells, I believe Twitter is already a protocol, we just call it the Twitter API. It's not an open protocol, of course, and its domain model is fairly anemic [1], especially compared to that of Facebook [2][3][4]. But in my opinion, this is what the author is trying to say: Twitter could have been a place where people interact with structured resources created and consumed by other apps.

It's a possibility, especially since Facebook became that place instead. Ultimately, Twitter didn't because they wanted to focus on driving more traffic through their first-party app (presumably as a captive client on which they can eventually display ads), and because they focused on cultivating a community (like Medium, Tumblr, LiveJournal) rather than a resource ecosystem.

[1] https://dev.twitter.com/rest/public [2] https://developers.facebook.com/docs/graph-api/reference [3] https://developers.facebook.com/docs/sharing/opengraph/using... [4] https://developers.facebook.com/docs/sharing/opengraph/objec...