Today my Switch received 6 different marks on the screen, here is how.
I was putting a screen protector on and laid the plastic film on top of the screen so that I could position it right, during this process the screen somehow now has 6 permanent marks that look like smudges but won't come out. There's also marks on the bezels which I assume might be from the dock.
All I did was lay a sheet of thin plastic, the stuff you peel away from a protector when you're about to apply it. I'm phoning Nintendo tomorrow to get a replacement, then I'll be putting a protector on without daring to touch the screen in any way.
For comparison, my S7 Edge has been in the pockets of lots of coats, trousers and tumbled down to my carpet a few times and the screen is flawless. The Switch had a flat piece of plastic film laid on top of it for a few minutes -- permanently marked.
A screen this fragile should not be on a portable product.