Earlier quoted context omitted.
Finally back at a computer, can reply to this in full now: >I would disagree, You can make Text-only links look fairly harmless too. The issue is more often that people do not look at all, even in text-mail, what the link points to, not that they can't see it (plus you can hover and the browser still shows the URL once you open it) It would be difficult to argue that it's not at least more difficult to phish people w…
For the vast majority of people html formatting is better and more efficient for their communication needs. Bold and highlighted text, section headers, tables and inline images are all very very standard and useful things to have in emails. These are not niche use cases.
Inline images are not useful, just attach them. Leave your giant signature with your company logo at the door.
What's left is section headers and bold text. Use asterisks for emphasis and # for section headers and you can communicate quite effectively. We seem to manage pretty well here on Hacker News without most of these features, wouldn't you say?