After figuring out a good non-destructive Mohs hardness tester isn't cheap, I decided to just go with it, assuming the display window was acrylic glass. It either is (I'm pretty sure it is), or it's close enough that PolyWatch works really well on it. After just polishing the window a few times, it was amazing how clearer it became. It must have had lots of micro-scratches and/or pitting in it. So after that, the deeper scratches were worked on. The window appears to be pretty thick so I don't think you'd damage it, but my finger got tired at polishing it before all the scratches were out. But they were definitely much less prominent afterwards. Note that the display module does move around a little bit; don't use too much pressure, I think it could be caved in if you go all in on it. The scratches are pretty light now though, and it's not easy to see unless it's at an angle. I hadn't realized the substrate below the LCD was actually somewhat reflective and actually somewhat of a nice textured greenish plate. The LCD characters now clearly "float" (they're above the reflection layer in a sandwich of multiple layers, science stuff) over the substrate, and you can see their shadows now. I highly recommend PolyWatch for use on the Neo 2 (presumably the Neo has the same display module), and it might be considered for others. The display window now looks almost new, after I wiped it off with a lint-free cloth.

My PolyWatch came with what appears to be a Dremel-type buffing attachment. I don't have a Dremel, but you might find it easier to use if you do and have the buffing attachment for it.