The frequency of the effect is very low when the lines are close to horizontal, and increases the more they deviate from horizontal. It's therefore a variant of the staircase pixelation effect on sharp edges which aren't perfectly horizontal or vertical, very probably exaggerated by oversharpening. When you say it's still there in the RAW file, that probably means that whatever the default sharpening is that's being applied to process your RAW file into something visible is still too much for this particularly critical kind of high contrast thin detail. Look again, turning the sharpening right down to zero, and then seeing how much you can increase it before the effect appears.