How should I format plain-text emails to make everyone happy

I prefer reading and writing emails in plain text. My emails are presented and composed in 80-character fixed-width-font windows, and I love text messages that are properly quoted (with “>”) and marked up with ASCII. Like in the olden days…

However, I acknowledge that the world has moved on, and many people now read email on tiny or large screens that require text flowing, and they prefer proportional fonts. Traditional plain-text emails with hard newlines after 78 characters don't work well for them: Either the newlines appear in odd places, or the text is reflowed (badly) despite the hard newlines.

My question: How should my plain-text email be formatted to make them happy, without breaking the experience for plain-text users like myself?

I know about “format-flowed” (RFC 3676) which allows marking plain-text paragraphs as reflowable while keeping the classic sub-78-chars-per-line appearance for old clients. Unfortunately, it is not supported by many email clients that would benefit from them most (including many web mailers).

Many emails clients simply generate very long lines (without newlines) that are intended to be displayed as flowed paragraphs. Is that a universally accepted standard now? I can see three issues with it:

1. RFC 5322 limits the line length to 998 characters. What's with paragraphs that are longer than that?

2. Can text quoted with “>” be reflowed at all?

3. It breaks old clients that do not know when or how to reflow very long lines.

Is there any other standard to mark plain-text emails as reflowable?

Note that I am quite flexible in what I generate. My email client is extremely configurable to start with, and I can hack it where I need to (I'm using GNUS in Emacs).

Also note that this question is not about HTML-formatted emails. I'm aware of them, I can read them, I can even generate them if needed — but this question is strictly about plain-text emails.

Finally, receiving email in any format is not an issue for me. GNUS can display all plain text formats (as well as HTML-formatted emails) satisfactorily.