Mastodon Does Microformats, ActivityPub Does Check-Ins and Travel Plans by Ton Zijlstra (zylstra.org)
I hadn’t really looked, but it turns out that Mastodon has incorporated microformats. It has h-feed and h-card, h-entry (a status), and h-cite (a boost). Plaint text properties (p-), e-content, and link properties (u-) are implemented. Indeed, they all surface when looking at a profile’s HTML so...

Mastodon Does Microformats, ActivityPub Does Check-Ins and Travel Plans: https://www.zylstra.org/blog/2022/11/mastodon-does-microformats-activitypub-does-check-ins-and-travel-plans/