Исповедник, разумеется, есть пруфы:
1. Из статьи, в сотый раз уже пишу: "When Voldemort realised that the young man had a position at Hogwarts, he took immediate possession of Quirrell, who was incapable of resisting.
While Quirrell did not lose his soul, he became completely subjugated by Voldemort, who caused a frightful mutation of Quirrell’s body: now Voldemort looked out of the back of Quirrell’s head and directed his movements, even forcing him to attempt murder. Quirrell tried to put up feeble resistance on occasion, but Voldemort was far too strong for him."

2. Из Кубка огня: "Only one power remained to me. I could possess the bodies of others. But I dared not go where other humans were plentiful, for I knew that the Aurors were still abroad and searching for me."

То, о чём я писала и чего не было в книгах, не хэдканон, а утверждения, основанные на доп. материалах. Можете принимать их, можете не принимать, но это то, что было в голове автора, когда она писала книги. И Регулуса это тоже касается.