Ah, but earrings reject on normal healing people, too. It's a matter of what is easier for your body, actually. If it's easier to reject the foreign object then it'll push it out, like a surface piercing usually is. But if the easier route is to heal around it, like a lip ring, then your body will heal around it instead of trying to eject it. It's probably just a matter of figuring out how deep it would need to be planted in you and whether or not that could be done safely. If it was done sort of like a dermal anchor where you have essentially an L shaped incision and it's slipped into the little foot of the L that might make it harder to reject since your body would need to push it to the side and then out in order to follow the path of least resistance, which it's unlikely to do.