If you like thinking about things in terms of how they work:
Fedi has a concept of a "post". A post always has an html representation, which is what gets disseminated (and which your Mastodon client will display). It also has a canonical URL that you can visit to see it (if the post is publicly visible). What you see there can be richer than the disseminated representation.
(The disseminated representation also contains various ancillary bits of data: some of them standard (e.g. "this is a reply to post X", "this mentions users A, B, and C") and some nonstandard (e.g. "this quotes post Y").)
If you want to see the disseminated representation, add `.json` to the post's URL (technically you should do something more involved, but this seems to also work with all instance software I've seen).
