Visible "square mesh" on Retina Screen

I bought a new Macbook Pro Retina Display last month (running El Capitan, version 10.11.4) and ever since I got it I have noticed a very faint grid or mesh over the entire screen. It isn't readily visible and I've been laughed out of two authorised Apple resellers (I live in Uruguay) because they can't see it, and diagnostics test come back negative. Two friends of mine who actually took their time staring at my screen have seen it however. What's more, I'm certain I'm not imagining this abnormality because I happen to own a second Macbook Pro Retina Display that doesn't have this issue.

The grid I see doesn't ruin the screen, but I'm a designer and usually spend hours working with very fine detail and this grid is becoming more and more annoying. The fact that it shouldn't be there and I just paid 2,500 dollars for this computer should be enough to warrant a solution for this problem. I have looked at the screen with a magnifying glass but then all I see are the actual pixels divided into red, green and blue. This couldn't be what I see with the naked eye unless I had bionic eyes, right? I have no way of contacting official Apple support from here…

The biggest problem so far has been capturing a photograph of the elusive fault, but I managed to take one that (when magnified) shows it pretty well. Remember, I see this ALL THE TIME with my naked eyes!

Image:

One more thing: a tech-saavy friend of mine suggested that it could be possible that new retina displays might be manufactured differently, and that light wave frequency could behave strangely with the way my eyes (and some other people's eyes) perceive what's happening on the screen. I really hope this isn't right, but if there is anything to what he says, shouldn't I get a solution anyway?

Thank you.