For thousands of years prior to the invention of HTML email, back unto the ages of cuneiform on clay, people managed to express themselves. Entire competing schools of rhetoric developed to teach people how best to express themselves, long before any form of electronic mail existed. Some of those schools focused on eloquence and interest, others on brevity and clarity, and those were both possible with plain text written by reed pens and ink on papyrus. I wonder whether relying on HTML for one's expression is really better than cultivating a writing style that suffices to convey one's thoughts independently of the medium used.

That's great because mail readers have supported threading for decades. It's pretty essential for using a mailing list.

Most mail readers support it, but not Microsoft ones. Somehow they managed to ruin this simple feature. This caused Google to reinvent it in the early 2000s and announce it like it was an innovation of their own.

I’m almost certain thunderbird soft wraps plaintext emails when composing rather than inserting actual line breaks for that reason.

Besides, shorter lines are easier to read and parse; I’d take an 80 columns width text anytime over a 120+ cols, like more and more people tend to use.