OK, this is a little embarrassing. I have poked and prodded the +Quote button a bunch of times over the years and haven't figured out what it does or how to use it.
It just toggles back and forth between +Quote and -Quote while a quick banner message flashes at the top:
Having done that and clicked around I can't see any difference.
It just toggles back and forth between +Quote and -Quote while a quick banner message flashes at the top: