Harry não é um Horcrux.
Como confirmado pela seguinte citação da JKR (que copiei de esta resposta do primeiro e único @ Sonstherincess):
"Here is the thing: for convenience, I had Dumbledore say to Harry, "You were the Horcrux he never meant to make," but I think, by definition, a Horcrux has to be made intentionally. So because Voldemort never went through the grotesque process that I imagine creates a Horcrux with Harry, it was just that he had destabilised his soul so much that it split when he was hit by the backfiring curse. And so this part of it flies off, and attaches to the only living thing in the room. A part of it flees in the very-close-to-death limbo state that Voldemort then goes on and exists in. I suppose it's very close to being a Horcrux, but Harry did not become an evil object. He didn't have curses upon him that the other Horcruxes had. He himself was not contaminated by carrying this bit of parasitic soul."
source
Ele só tem um pedaço da alma de Voldemort de alguma forma 'ligado', parasiticamente, ao seu próprio. A poderosa Magia Negra que cerca uma verdadeira Horcrux não está presente nele: Voldemort nunca passou por esse processo com ele, já que essa divisão de almas não foi intencional. É essa Magia Negra que protege a Horcrux de danos por magias de baixo nível, então não há razão para Harry estar tão protegido de magias como as verdadeiras Horcruxes. Faz sentido que um fragmento de alma sem magia especial não tenha nenhuma proteção especial; parte da magia envolvida na criação de uma verdadeira Horcrux deve ser criar tal proteção.
Do Guia dos Trouxas para Harry Potter :
A soul fragment bound to an object, a Horcrux, is proof against ordinary magic, even magic as strong as that produced by an extraordinary wand. (At least, evidence is that Dumbledore believed so, and we have seen nothing against that.) The soul fragment within Harry is not actually bound to him, but is merely clinging to his own soul, and as such is only as strong as Harry himself; if Harry's soul is separated from his body, the soul fragment is detached and vanishes.