It looks as if you have not followed the argument. I guess you can't, not without losing too much. Yes, it is about degrees of moral standing. Your essentialism aims for an absolute moral law. But morals are decided, not found, oughts, not is's. That your proposal gives at least the same rights to a cyst as to a person is damning.

Even if you grant that a being is a member of the human species, that does not mean they count as a person or as a moral agent.

I never suggested it did. I don’t know why everyone is coming at me with straw mans after I gave a very specific argument that addressed this very point. I will say it again. Not all human beings are persons, and not all persons are necessarily human beings. The obvious rejoinder to my position, prima facie, is the personhood-style arguments; but I think they fail for many reasons (which I will skip over for now) and that the best way to ground rights is in the Telos (ps: I know that’s a dirty word now) of a being such that it marks them out as a person (as opposed to being currently a person). In short, I take a hybrid view between animalism and these personhood-style positions.

children's legal status is also different

When talking about abortion, this point would imply that, it is possible that, an unborn child’s legal status is that it can be killed. At that point, it doesn’t a legal status; which is what a personhood-style position is going to want to argue.

People's status as an agent may change if they go into a permanent coma, we have next of kin rules, waivers, and even (arguably) the ability to extend our capacity for consent after our death with organ donation and wills.

These are all good points. I would say that that:

1. The morally relevant differences between these examples and abortion is NOT that people’s status’ change but, rather, that, when properly understood, they are toto genere different moral dilemmas.

2. Euthanasia does not involve, when properly understood, the killing of an innocent person in the sense which happens in abortion: the person who wants to die is giving consent from a rational state of mind, whereas the unborn child is not. I think it is implied in “innocence” that the person is not partaking in whatever is in question; but, if you want, we can just tack-on “it is wrong to kill an innocent person who isn’t properly consenting to being killed” (and, yes, “properly” is doing a lot of work here).

3. Killing a person who is in a permanent coma, who had not properly consented to being killed prior to comatose, is being murdered; and, no, a family member should not have the power to command their execution.

4. Consent for organ donation and wills are examples of consent which are properly crafted during a rational mind-set; and so this is perfectly fine. However, to use a person’s dead corpse to experiment on or donate in ways which were not consented would be immoral; even if it could save someone else’s life.

Moreover, unfertilised gametes and severed limbs are recognisably of the species homo sapiens and are not treated as moral persons

Unfertilized gametes and severed limbs are not members of the human species: they are parts of humans.

The unfertilised gametes, severed limbs and dead bodies aren't even conscious, the former two have no moral agency and the latter are treated as moral agents (as if they were alive) in a limited fashion.

According to personhood-style arguments, I think you bring up a good point here (although I know this is not what you are intending to convey) that dead bodies would not have any rights whatsoever; because rights are associated with actual personhood—current persons. So it should be, under their view, morally permissible to do anything to the dead corpses (such as having sex or using it as a punching bag).

It only makes sense to give it EVEN PARTIAL respectful treatment, other than as a mere subjective taste, if one is thinking about it like an Aristotelian: that being was a member of a species which marks it out as a person, and this means I still have to respect this being even after death.

To summarise, each of those entities counts as a member of the species homo sapiens, but they are not a moral agent

What is a moral agent is different than what is a person; and the former has nothing to do with grounding rights. Moral agency is about which agents are held responsible for their free acts and to what degree; and personhood is about features of the mind which ground certain innate rights.

Then, Michael, you are literally arguing that there is no point at which a human being acquires rights.

I want to here, Banno, your moral theory. Explain it, so I can see what I am working with here. How does the graduations of rights work?

No point. If you can't see that a cyst has less standing than Mrs Smith, you are not even in the same game.

I think what's trying (imo, quite badly) to do is point out that your argument (i.e how you would assess the question yourself) is inapt for much of a pregnancy.

I realise it's likely you will side with the mother regardless, But i think that's what he wants you to admit.

If the idea that is that, stepping back, in the round, the mother takes moral priority, does this include up to the anticipated date of birth? Timothy nearly got there, point out a human is also a clump of cells.

But there is obviously also a difference between a blastocyst and a fetus. But also, a fetus and a baby. Which means what to your version of the argument? The reason most want an 'essentialist' account of personhood is to demarcate at which point a 'clump of cells' gets moral priority (you may bite the bullet of late-term abortion. I don't, so this isn't obvious to me). This is because we don't make decisions 'in the round' or 'stepping back'. We make them on the actual facts (i.e how far along is this fetus at hte time the abortion has been proposed).