[stephenr]

The RFC's are just about defining the Media Type 'text/markdown' aren't they?

Just because they used to be called MIME types and were designed for email, I wouldn't treat those RFC's as being about email support specifically.

[zwp]

Sure, it could be used elsewhere. OTOH 7763 calls out email as a use case three times and in section 5 Examples "email attachment" is the only example.