That sure *looks* like the usual ghosting artefacts, made more obvious by night mode, even with the fancy tricks used by the PW4/KOA2/KOA3 (speaking of bleed-through).
The grid patterns might be the (ordered) dithering patterns being made more obvious by night mode, again. This is either more obvious or less obvious than the ghosting, depending on what's on screen, and depending on how exactly the dithering is implemented. My lack of first-hand experience with these devices means I can't actually tell you if that should ever actually be visible on a Kindle.
I can generate torture tests that do exhibit those things, though
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