I couldn’t find anything about this problem online, even though it seems like an extremely basic flaw of the layer system: there seems to be some kind of alpha/multiplication problem when erasing polypainting from a layer. On the left side, I’ve erased from the blue paint layer to show the metal texture under it. This creates dark rims around my strokes and after exiting the layer, the transparency doesn’t look the way it should. Only after filling the blue paint layer with RGB Intensity 100%, the dark rims go away. But this is a solution that works only when a layer is meant to be single color. Am I doing something wrong when erasing layers? I simply hit “Alt” and brush away with only “RGB” on (not painting materials).