I have some fine scratches too, and a couple of smaller slightly deeper ones. I do not recall how i got them either.
I hate having skins and stuff on my phone/tablets either, but my friend surface pro 128 is in pristine condition.
I believe I took care of my Surface fairly well. I did do a lot of traveling with it...so i think the scratches could have came from sand when I was using it at the beach and when i put it back in my backpack...
oh well, it might affect my resale value a little bit, but not planning to get rid of this until at least a year from now...so the resale value will be hurt either way.