I have a keloid in one of my ear piercings (I have 6 holes in my ears) it was done when I was 14 had the correct care and still scarred.
I've had my nose done twice, neither time did it scar nor do I have keloids but they took forever to heal and I took them out both times, the second time I conceived the night I was pierced so pregnancy hormones did play a role there, I tried for a year and it never healed
I have 2 tats, one in color which I've had 8 years, the yellows and pale greens have faded some, the dark greens, oranges and red have not, no scarring at all with them, and I'm actually planning on covering the other which has no color it's gray and black
My dh also has a large arm piece and he has scarring from insect bites but none from his tat.
That said I will be going back to the guy who did my first years ago to do my back/cover piece he works almost exclusively on dark skin (he's based in the Caribbean) and does excellent work.