It surprised me to see how common that was. And I know Larry Miller picks them up that way. It may be fine to do so, but it sure makes me cringe a little to see it.

When I started playing, I never used the stops to lift or carry the box. Then I saw several people do it, and thought it was okay. However, I won't do it again. All it takes is a little sideway pressure to damage the stop mechanism.
Plus jamais!

I dunno. I think it's fine. My Savoy accordions are built like tanks.

Mais me, I grab em like this chere.