In many ways, a moral compass seems to describe our genetic disposition for social fairness, traits which we share with other primates .. ours being genetically the most advanced. And if this compass does have a genetic basis, then it follows that the underlying traits may be stronger in some people and weaker or absent in others.
This could explain a lot. For example, at the extremes, folks born with a heightened sense of morality (a very strong moral compass) may experience even petty social slights as highly offensive. In others, this heightened sensitivity might cause them to overestimate the offensiveness of their behaviors toward others resulting in excessive guilt.
People with weak or a highly suppressed moral compass wouldn't experience guilt the same way we do. For most of us, guilt is a strong self-correcting feature that influences our social behavior. Guilt is uncomfortable. It motivates us to either change behavior patterns or to avoid that which causes us guilt.
At the other extreme, if a moral compass is a durable human feature, then even people who learn how to ignore their compass must also suppress the guilt associated with it. This should create behavioral tells that can distinguish people who ignore their compass from people born with a weak moral compass. The rare person who is born without a moral compass has no capacity for guilt. These are true and dangerous sociopaths for whom moral actions are merely calculations coupled with mimicked social behaviors.
The idea that any human behavior could be traced to genetics (or what we might call instincts in other animals) isn't an entirely new idea as these things go, but recent research in this area strongly supports such connections. And it makes sense. If you ever observed a baby cry when another baby takes a toy from them you can see that crying behavior isn't learned. It's natural. It is instinctual. The actual hurt that causes those tears is a violation of social justice. Injustice creates emotional consequences which, on the victim's side, is painful and potentially harmful to their well being.