(The title says it all, really!)
With the the Frame Buffer in MODE 7, Shift+F7/F8/F9 do COPY, left cursor and right cursor rather than select white, flash and no flash. Shift+F1-F6 work fine, though, selecting colours.
I'm not sure if it's a keyboard or frame buffer problem, but it's clearly related to the Pi Frame Buffer.
This is on the latest hognose-dev commit 8ed9d34.