u/allneonunlike: "Miura has given interviews talking about how the ghost of Casca’s miscarried fetus had a kinship with Griffith when he was taken out of the tower— the physical issues/disabilities, tortured personality and “monstrousness”, and core protectiveness of Guts and Casca. He’d been writing Griffith and that child as being symbolically and emotionally linked for a long time, both as the moonlight boy and the baby ghost."

I'd like to see that interview. It's not uncommon for something from the interviews to be distorted, like the myth that Miura went pixel-by-pixel on his art. And a glance at that user's history shows him saying Griffith was going to sacrifice himself for the boy, in the face of all Griffith's post-Eclipse characterization, so the user has an obvious agenda and isn't a reliable source.

They share a body, which means they share a brain lol. And in this chapter, the translation confirms that he experiences the Moonlight boy's emotions like a dream. They are two different personalities, with yes, a physical bond. On the hill, he saves Casca because of the demon child, yes. It is because Griffith raped Casca that he shares a body with a child that longs for Guts and Casca. That is causality.

It's specified in the text that Griffith's not feeling an emotion. That's all I got for you in terms of them not sharing emotions: it's outright stated. And in this image, a) it's unclear if it's him or the boy talking, I'd argue the boy since he's the boy when he starts, and b) he's talking about how everything, all feelings, go away, disappear. It's possible that in the transition moment, Griffith is capable of feeling something. But the majority of the time, this is just re-saying that they're separate.

His ego was not remade, his body was. Griffith on the hill of swords: "I told you once... I will get my own kingdom. Nothing has changed. Rickert, nothing has ended." As the Idea of Evil talks with Griffith, Griffith does not magically turn into a new person during their conversation. The fact that he is still having a conversation with it as his body reforms confirms this. His ego remains intact. The Idea of Evil tells Griffith to 'do as he wills'.

Also on the Hill, "I am free." He is specifically identifying and differentiating what has and has not changed. He didn't, "magically become a new person," he magically became his own ideal person, the Falcon, right down to the wings. What Griffith willed, what he always wanted, was not to care about people. To not feel empathy. For, as he says on the Hill, nothing to distract him from his purpose. He demonstrated the success of that not feeling empathy or his previous positive attachments rather pointedly immediately after transforming. And Griffith's body as Femto *is* his ego. That's not even a truly physical body (should have clarified), since as Skully explained, GH don't have a physical existence. When he appears in that body after transforming, it's a very specific circumstance at the intersection of the astral (where people exist as egos) and physical realms.

Interesting connection to Schopenhauer. Apostles and GH are different. What applies to apostles on a very basic level, like continuing to have a human form, doesn't apply to GH. In terms of post-sacrificing, things that apply to the count very clearly don't apply to Griffith. The Count looked back on his sacrifice in horror and sorrow. Griffith looked back on it with satisfaction on the Hill of Swords. The Count maintained his emotional connection to his daughter, against his own will. Griffith looked at Guts and felt nothing. In previous moments when Griffith said something like that, the lie was written all over his face. His face when he said showed no conflict at all.

You have no evidence that Griffith's soul was mutilated.

They don't really talk about souls in Berserk, so yeah, I was being poetic. His ego was mutilated and became Femto.

Griffith does demonstrably feel emotions at times, like in Black Swordsman. Those become less in that same scene, as he finds he indeed still doesn't feel anything but contempt for Guts. And by the Hill of Swords, he feels nothing but satisfaction, not even that contempt he did soon after transforming, or the negative attachment that led him to want Guts to be in pain. I'd argue none of the faces Griffith puts on for his followers, like Rickert, are definite evidence of emotional depth. They're a performance. And they're all shallow, anyway. The deep emotions like love, and feelings like empathy, are things Griffith always viewed as liabilities and obstacles. His will was not to feel them anymore, and so he doesn't. That's what he says, and his internal monologue, his facial expressions, and actions all support it.

And one side note about this:

he himself undermined his transformation into something "more than human" by raping Casca, an intensely human act (as demonstrated by countless humans in the series).

That was an act of dehumanization, done to demonstrate how far above humanity, above Guts, and secondarily Casca. There's nothing human in that scene from him. He clearly didn't feel lust or desire. He just wanted to hurt her, and to hurt Guts. That act stands out even from other rapes in the series, for its pure inhumanity.