Devil’s advocate: what about the posts and comments I’ve made via Lemmy? They could be presented as files (like email). I could read, write and remove them. I could edit my comments with Microsoft Word or ed. I could run some machine learning processing on all my comments in a Docker container using just a bind mount like you mentioned. I could back them up to Backblaze B2 or a USB drive with the same tools.
But I can’t. They’re in a PostgreSQL database (which I can’t query), accessible via a HTTP API. I’ve actually written a Lemmy API client, then used that to make a read-only file system interface to Lemmy (pkg.go.dev/olowe.co/lemmy). Using that file system I’ve written an app to access Lemmy from a weird text editing environment I use (developed at least 30 years before Lemmy was even written!): lemmy.sdf.org/post/1035382