Thanks for the heads-up re the navigation and quotation keys. I can see y'all's point about quoting the actual text seeming to be a good solution and a smaller task than inverting from html to markdown.
For my purposes, q + j/k works well enough. Even if y'all got your way, with the hover-quote grabbing the rendered text (just as you'd get by copy-paste), you've got hazards like this one from @alistaire's opening sentence, copy-pasted here using > for a quote block:
gets escaped to >
or copy pasting into a [quote] block:
You'll really want to quote with all the markup and for that, only the behavior of the q shortcut seems adequate:
What I find annoying is that when I use the shortcut (attempted just now), it doesn't drop it in my existing edit but instead constructs a new post, so I need to copy-paste that back into my in-progress edit (assuming it wasn't lost along the way). So when I'm quoting from multiple posts, it'll be a hassle.
(Btw, I'm using keyboard-button markup from SO above.)