[Moru]

Markdown is designed to be readable without encoding it as HTML though, so is nicely readable on old email clients too.

[krapp]

Sure, but then it's just plain text, and plain text could be perfectly legible before Markdown came along.

The only tangible benefit Markdown provides is letting people write HTML who don't like the aesthetics of HTML tags.

[swalladge]

The idea is that it gives a standard for semantic markup that can be read as plain text. Lists, highlighted text, block quotes, etc. that is all plain text but easily parsed by humans.