Hopefully the final update:
I got my replacement Kindle today and it has the same problem towards the top left side. Thankfully it's out of the realm of actual usage - I would probably have never noticed if I wasn't checking the whole thing - and the original actually has it in the new spot too, so I'm pretty happy with the replacement.
One minor cosmetic difference is that the keys don't seem perfectly centered as they are on the original. You have to have stupid attention to detail to even notice it though! I get the impression that minor discrepancies in the front and back panels are just inherent to the click together design.
The guy on the phone told me to keep the charger and cable, but they sent another cable with the replacement. Does this mean I now have a spare?