So I've also been having problems with swiftkey doing what I thought was a phantom press or lifting of my finger around the "j" or "k" keys causing weird words popping up such as "for now" becoming "I is" and "only" became "k input" - referenced from my email to swiftkey support.
Tonight I was cleaning my screen with a VERY lightly damp microfiber cloth and right in that area of J and K keys the dampness looked different from other parts of the screen. Not sure how to describe it, but it's not scratches, just a different texture if you will.
It happens to be exactly where my thumb rests when I'm scrolling thru pages, apps or what have you. I think I've worn off part of the coating that protects the phone. I can't see it when it's "dry" even shifting it under the glare of my lights. I think this is a warranty issue for sure, but I can't wait weeks or months for them to repair it, I'll have to go out and get a new phone to have something that works and I won't deal with a cheap phone for that long, a week or two is OK, but not months!
So you guys might try doing what I did with the cloth and see if you see the same thing. I'd be interested to see if more of us have this issue.