Quoted from rotordave:All hinges (should!) have a thick washer between the body and the hinge so the hinge should never touch the side rail. There is a few MM gap between the two.
rd.
They shouldn't touch, but when dropping the head down most people are on one side of the machine which can lead to the head torquing and it can rub. I'd just be more concerned with paint than powder, paint is so much more easily damaged. the hinge would act like scissors if it made contact just shearing off large flakes of paint. even rings on someones hand can be an issue.
That being said, I'm not doing either to my machines. I just put it up as a potential issue to watch for.