This would let you quote several posts on one reply. I've seen it in other places.

Right now I have to cut and past and half the time I lose the partial reply,

Come, Luke.  Join me in the dark side.

This is already available in the new site, r.rpol.net.  The new site doesn't open a new window when you reply or quote, just an edit section below the messages.  The messages above still have a 'quote' button, and clicking it adds that message (in quote tags) to your ongoing edit.