alt Hacker NewsThe definition of "text" itself is quite vague. Is a code sample text? What about a series of code samples intercalated with common language descriptions? What about a numbered list? What about a poem?
Also, just because I send some text as HTML doesn't prevent in any way the receiver from formatting that however they want. I'm just adding some display hints, that their email client may or may not ignore.
What about it? Your e-mail composer will tell you when you put something in your message which isn't plaintext and offer to convert your message to HTML for you to keep writing it.