O sacrifício só fez com que o Lorde das Trevas não tocasse Harry.

O sacrifício de Lily só fez com que o Lorde das Trevas especificamente não pudesse tocar Harry - não funcionava em todas as pessoas que significavam dano a Harry, ou os seguidores do Lorde das Trevas, apenas o próprio Lorde das Trevas. No cemitério, o Lord das Trevas diz que ele não podia tocar Harry depois que o sacrifício de Lily o protegeu.

“You all know that on the night I lost my powers and my body, I tried to kill him. His mother died in the attempt to save him – and unwittingly provided him with a protection I admit I had not foreseen … I could not touch the boy.”
_{^{- Harry Potter and the Goblet of Fire, Chapter 33 (The Death Eaters)}}

Rabicho, no entanto, toca Harry sem nenhum sinal de estar sofrendo com o contato com ele, apesar de ser um Comensal da Morte a serviço do Lorde das Trevas.

“Harry could hear shallow, fast breathing from the depths of the hood; he struggled, and the man hit him – hit him with a hand that had a finger missing. And Harry realised who was under the hood. It was Wormtail.”
_{^{- Harry Potter and the Goblet of Fire, Chapter 32 (Flesh, Blood and Bone)}}

Isso acontece antes que o Lorde das Trevas use o sangue de Harry na poção para construir seu novo corpo, permitindo que ele toque Harry, então o Lorde das Trevas seria incapaz de tocar Harry, mas Rabicho, que trabalhava para ele e agia. em seu nome tanto quanto Quirrell, podia. A única razão pela qual Quirrell não podia tocar Harry era que a parte principal da alma do Lorde das Trevas estava nele na época.

“But why couldn’t Quirrell touch me?’

‘Your mother died to save you. If there is one thing Voldemort cannot understand, it is love. He didn’t realise that love as powerful as your mother’s for you leaves its own mark. Not a scar, no visible sign … to have been loved so deeply, even though the person who loved us is gone, will give us some protection for ever. It is in your very skin. Quirrell, full of hatred, greed and ambition, sharing his soul with Voldemort, could not touch you for this reason. It was agony to touch a person marked by something so good.”
_{^{- Harry Potter and the Philosopher's Stone, Chapter 17 (The Man with Two Faces)}}

Também funciona apenas na parte principal do soul do Dark Lord - não funciona nas Horcruxes. Harry tocou e interagiu com o diário, também antes que o Lorde das Trevas se tornasse imune ao seu toque.

“Oozing back out of the page, in his very own ink, came words Harry had never written.

‘Hello, Harry Potter. My name is Tom Riddle. How did you come by my diary?”
_{^{- Harry Potter and the Chamber of Secrets, Chapter 13 (The Very Secret Diary)}}

Era apenas a alma principal do Lorde das Trevas que não podia tocar Harry, e quando ele possuía Quirrell, isso também tornava Quirrell vulnerável ao toque de Harry, porque o Lorde das Trevas compartilhava seu corpo.

Isso é explicado por Dumbledore quando ele visita Harry na Ala Hospitalar após o confronto com Quirrel:

“But why couldn’t Quirrell touch me?”

“Your mother died to save you. If there is one thing Voldemort cannot understand, it is love. He didn’t realize that love as powerful as your mother’s for you leaves its own mark. Not a scar, no visible sign ... to have been loved so deeply, even though the person who loved us is gone, will give us some protection forever. It is in your very skin. Quirrell, full of hatred, greed, and ambition, sharing his soul with Voldemort, could not touch you for this reason. It was agony to touch a person marked by something so good.”

Das palavras em negrito, parece que o efeito de queimadura foi único para Quirrel / Voldemort porque eles estavam tão cheios de ódio. Parece que foi especificamente o choque de ódio e amor que produziu o efeito de queimadura.