I’m going to assume you’re saying surgical scars?
Basically it depends on each person’s ability to heal and form the new tissues (aka skin) in place of it. Some genetics can lead to keloids (bumps where the skin heals) and some people don’t.
But as with most things on our body it’s in constant motion so healing will probably not be perfectly straight which is probably okay too since we need our healing to also be as moveable and flexible as our body.
Sometimes the new tissue tends to be stiffer
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