On Return of the Obra Dinn's dithering specifically, here is the original developer blog on its dithering: https://forums.tigsource.com/index.php?topic=40832.msg136374...

It's intended, aesthetically, to remind you of Atkinson dithering (https://en.wikipedia.org/wiki/Atkinson_dithering), a variant of Floyd-Steinberg dithering often used in graphics for the black-and-white Macintosh.