Se um Horcrux vivo fosse morto “normalmente”, eles deixariam de ser um?

Sim

Eu comecei a digitar uma comparação gigante entre Quirrel, Nagini e Harry, mas não acho que precisaremos disso aqui.

Como você destrói uma Horcrux?

‘It has to be something so destructive that the Horcrux can’t repair itself. Basilisk venom only has one antidote, and it’s incredibly rare' - 'phoenix tears,’ said Harry, nodding.

Então, por que se Harry morresse normalmente, ele não seria mais um horcrux?

Por causa dessa citação de Rowling.

Q: When Harry was stabbed by a basilisk in the Chamber of Secrets, since he was a Horcrux, shouldn't it have been destroyed then?

JKR: I have been asked that a lot. Harry was exceptionally fortunate in that he had Fawkes. So before he could be destroyed without repair, which is what is necessary to destroy a horcrux, he was mended. However, I made sure that Fawkes wasn't around the second time a Horcrux got stabbed by a basilisk fang, so the poison did its work and it was irreparable within a short period of time.... I established early in the book, Hermione says that you destroy a Horcrux by using something so powerful that there's no remedy. But she does say there is a remedy for basilisk poison but of course it has to be administered immediately and when they stab the cup later - boy I'm really blowing this for anyone who hasn't finished the book - there's Fawkes, is my answer. And thank you for giving me a chance to say that because people have argued that quite a lot.

Então aqui Harry seria destruído além do reparo, também conhecido como, ele iria morrer. A morte pessoal de Harry, foi a destruição que foi necessária para a remoção do fragmento de alma de Voldemort. Sua morte, não a presença de veneno de basilisco em seu corpo, que por acaso era essa causa particular de morte. Seu corpo ainda teria permanecido intacto, então, pelo menos para Harry, a alma era necessária para a alma de Voldemort permanecer ligada.

Eu não acho que um Avada ou um acidente ou Ebola, ou o que quer que seja, teria matado Harry enquanto ele ainda tinha aquele oitavo pedaço da alma de Voldemort dentro dele. Eu percebo que isso é diferente da sua pergunta, que pergunta especificamente se Harry tinha sido morto, mas eu não acho que Harry poderia ter sido morto por qualquer meio enquanto Voldemort ainda estivesse vivo.

Desde que o próprio Voldemort estivesse vivo, Harry não poderia morrer, porque Voldemort amarrou a vida de Harry quando usou o sangue de Harry (especificamente) na poção da ressurreição em Cálice de Fogo . Os encantamentos de proteção que fluíam através do sangue de Harry, através do sacrifício de Lily, agora fluíam dentro das veias de Voldemort, criando uma conexão recíproca e simbiótica entre Harry e Voldemort. De Relíquias da Morte :

‘But if Voldemort used the Killing Curse,’ Harry started again, ‘and nobody died for me this time – how can I be alive?’

‘I think you know,’ said Dumbledore. ‘Think back. Remember what he did, in his ignorance, in his greed and his cruelty.’

[...]

‘He took my blood,’ said Harry.

‘Precisely!’ said Dumbledore. ‘He took your blood and rebuilt his living body with it! Your blood in his veins, Harry, Lily’s protection inside both of you! He tethered you to life while he lives!’

‘I live ... while he lives? But I thought ... I thought it was the other way round! I thought we both had to die? Or is it the same thing?

[...]

‘He took your blood believing it would strengthen him. He took into his body a tiny part of the enchantment your mother laid upon you when she died for you. His body keeps her sacrifice alive, and while that enchantment survives, so do you and so does Voldemort’s one last hope for himself.’

[...]

‘What you must understand, Harry, is that you and Lord Voldemort have journeyed together into realms of magic hitherto unknown and untested. But here is what I think happened, and it is unprecedented, and no wandmaker could, I think, ever have predicted it or explained it to Voldemort.

‘Without meaning to, as you now know, Lord Voldemort doubled the bond between you when he returned to a human form. A part of his soul was still attached to yours, and, thinking to strengthen himself, he took a part of your mother’s sacrifice into himself. If he could only have understood the precise and terrible power of that sacrifice, he would not, perhaps, have dared to touch your blood ... but then, if he had been able to understand, he could not be Lord Voldemort, and might never have murdered at all.'

Deathly Hallows - Pages 567-569 - British Hardcover

Seria somente depois que o oitavo pedaço da alma de Voldemort fosse destruído e o próprio Voldemort estivesse morto que Harry se tornaria mortal e vulnerável à morte mais uma vez. Isso explica como Harry conseguiu sobreviver, digamos, ser decapitado, ou ter uma porção de doze toneladas do castelo de Hogwarts caindo em cima dele enquanto Voldemort ainda estava vivo? Não. Mas isto é o que cânon diz sobre a mortalidade e a suscetibilidade de Harry à morte em geral. A oitava porção da alma de Voldemort dentro de Harry deve ser destruída pelo próprio Voldemort, então eu acredito que a resposta para sua pergunta é não.

‘So the boy ... the boy must die?’ asked Snape, quite calmly.

‘And Voldemort himself must do it, Severus. That is essential.’

Another long silence. Then Snape said, ‘I thought ... all these years ... that we were protecting him for her. For Lily.’

‘We have protected him because it has been essential to teach him, to raise him, to let him try his strength,’ said Dumbledore, his eyes still tight shut. ‘Meanwhile, the connection between them grows ever stronger, a parasitic growth: sometimes I have thought he suspects it himself. If I know him, he will have arranged matters so that when he does set out to meet his death, it will, truly, mean the end of Voldemort.’

Deathly Hallows - Page 551 - British Hardcover

Poderia bem ser que Harry também estivesse protegido da mesma forma (seria um longo caminho explicá-lo sobreviver tanto quanto durante seu tempo em Hogwarts) - então talvez as maneiras que você sugere que ele poderia ter sido morto teriam de alguma forma recuperou ou de outra forma foi impedida.

A menos que haja alguma Palavra de Deus sobre o assunto, não creio que exista algo coberto nos livros sobre essa possibilidade.