[alanbernstein]

As the pro-plain-text post said: HTML, Markdown, JSON, LaTeX, and many other standard formats, are just plain text.

[ciphol]

It depends. XML is generally not human-readable, it's got way too much programming code in relation to the amount of human content. But a simple subset of HTML is definitely human-readable.

[mro_name]

No, not when it comes to what reading person they target.

Here text/plain is the only that works for e.g. my mother.