Looks like it wasn't assemble properly. If you just brought this recently and have an apple store closely be, I'd suggest pop in to see if they can fix this or exchange for a new one.
This is an area where dirt can get into the machine, so can't be good for long term health.
Yes! Samsung display, whow 6 :O, so if 2 had it i would then not risk at getting a bad display. In fact this is my 2nd the other showed Screen Persistance (LG).
My unit is the same so I would say it is normal. I read this earlier. I stopped by the Apple store and all eight of the retinas on display were identical.