Since when? I have never heard anyone say this in my entire life. I want emails to look good. So I guess people are different and we can't draw a simple conclusion about what people want from email?
The use of quotes in replies is also part of the article and is definitely a better way to go with bottom replies than the current default of top replies.
Which is my experience as well — it happens to be easy to quote.
The real quoting that email supports, the reply w/ embedded copy of replied email, is unaffected by html/plaintext choice.
I don't see how. It's just the same as plain text.
<div class="quote"> quoted content </div>
It's far better than trying to keep count of how many ">" are in play, and deal with the vagaries of soft linebreaks and hard linebreaks and wrapping of plaintext.
<div class="quote">
<li>Second</li>
<li>Third</li>
</div>
Without the surrounding `<ul>`. Luckily Thunderbird is smart enough to do this. I don't know about other clients.