Earlier quoted context omitted.
If only this RFC was well-known among the people who actually put stuff out on the Web.
If only that RFC didn't make it a hidden directory. I can think of a dozen reasons why hiding that folder is a horrible idea, and not a single one for why it would be a good thing to do.
There's zero guidance on configuring how URIs under `/.well-known/` should be served at all, is there? They just reserve/sandbox the initial path component for the URI schemes which support it. That's it. It's the developers' choice to implement it as a directory - hidden or otherwise - on a filesystem; neither RFC says they SHOULD or MUST be served in such a way.
(The updated RFC says "e.g., on a filesystem" in section 4.1, and mentions directories in section 4.4 in a way that, to my eyes, pretty much recommends against making it hidden)