Looks like cochineal scale. Hose it off with a very strong stream of water to knock it off. The red scale was probably the cohineal insect itself-that's where natural red dye comes from.

I've unfortunately seen too many mealybugs to know that this is something pretty different. I don't see an actual insect present, which makes me think it is either the plant repairing itself, some fungus, or just scarring from where the plant was damaged when I scrapped off the previous stuff…

I think this is exactly as you said, scarring from where you scraped of the scale. If you are not gentle, you end up damaging the skin.

Christopher