Everywhere. Most prominent are the unlock icon and the flashlight icon and the camera, but there are others; and some text.

Any time there is an area of flat color, or gradient color it really shows.

Have you tried taking it to an Apple store? I have an iPhone XS and I am 100% certain this doesn’t happen on mine.

Agreed. The reported behavior sounds more like defective hardware. I have my original iPhone X from launch and have used it for hours a day. Battery is a little beat up, but the screen is still perfect.