This is explained in the language without using self as the volition makes the kamma, the other 4 aggregates receives the results of the kamma. No need for an
ultimately existing agent to make sense of morality, although practically speaking, it’s much easier to talk morality using language of conventional self.
Buddhist morality also is higher level than mere socially constructed morality. A lot of superheroes have morality, as well as human justice system, based on “is” implies “ought”.
“is” here means what’s the reason for people to suffer. “ought” here means they should and deserve to suffer and no one ought to change it.
Whatever reason for people’s suffering, the ought is to help them if we can. That’s compassion. That’s a core teaching in the right thoughts of noble 8fold path.
This teaching is actually quite contradictory to worldly sense of justice and superhero morality. They believe in “is” implies “ought”. So a person who committed crime ought to be punished, and made to suffer by law or the superhero or the lone anti-hero like marvel’s punisher if the law fails.
But if they cannot see the link of people’s suffering to their actions in current life, they think that those people who suffer should not suffer. But we who learn about Rebirth would keep in mind that people’s actions are not limited to only bearing effect in this life, but also in future lives. Thus some suffering we have seen, maybe due to previous life unwholesome actions.
Those who believe in “is” implies “ought” then find it that if we can tell that this baby who died after being born sick, due to law of kamma, could be that she was a serial killer or something in the far past, so the baby deserves it. That’s repugnant to them because they believe in compassion too, just that their compassion is conditional, conditioned on that the person suffering is innocent.
It’s actually not the law of kamma that is problematic, it’s the view of “is” implies “ought”, which makes their compassion conditional. Upgrade the compassion to be unconditioned, then there’s no issue. This can also imply very hard to do thing. Like towards a person who just tortured oneself, the task for us is to be compassionate to them. Not to generate hate. Not to delight in the knowledge that they will suffer due to their current bad actions, but to have compassion due to it and think to want them to not create more causes of future suffering for themselves. Buddhist morality is higher level than superhero morality.