In The Power of Plain Text Catherine Powell wrote that we should send plain text in emails so that it can be easily re-used.
And she’s right. But you can go further. My company use a mediawiki for internal documentation and so I write emails in plain text with wiki markup (e.g. * for bullets) to make later pasting into the wiki straightforward. In fact, I write all of my plain text notes and bug reports in that format too, for the same reason. I use a wiki markup extension for Emacs and wiki2xhtml to render the mediawiki content as HTML for local viewing or easy printing.
Plain text might be Cinderella these days, but it can still go to the ball.