I sorta skimmed thru the thread, but have you taken it to a nearby Apple Store for a quick check? It seems like a manufacturing defect that can be addressed.
No, I didn’t go to the Apple Store with it. I could resolve it on my own with the help of a thin business card. I don’t think it is a manufacturing defect since the display performance/quality isn’t affected at all. It seems to be a residue from the coating process or some sort of that… didn’t have any issues since then.