Sadly the timing here is a bit off. Mastodon added microformats2 years ago; they’re actually now in the process of removing them in the 4.0.0 release. May not be intentional, may just be a casualty of switching the whole app to be an SPA that requires JavaScript (aka JS;DR), which kills their IndieWeb compatibility, since it means other web sites and IndieWeb tools can’t fetch Mastodon posts over HTTP directly any more. Sad.