what is a summary is in this context. are there docs on how (for example) RSS terminology maps on to ActivityPub terminology?
we have title, link and description as the three major components of a post.
in general in RSS, by convention, the description can have HTML and the others, not.
is what Mastodon does considered enough to get compatibility with other Fediverse platforms?
are you testing with Threads, for example? are they following what Mastodon supports?