Harry Potter always was a strange child, the Dursleys thought. He made strange faces at empty spaces and sometimes spoke to open air.
Harry, however, had a strange ability. If he came across something to which a dead person had an emotional bond, he could see that person’s spirit and talk to it. And so, even at the Dursleys, he regularly spoke to his parents, whose love bound them to him tighter than any chains.
The Dursleys soon grew very uneasy around him, because he suddenly knew things he had no way of knowing.
At Hogwarts, he is nearly overwhelmed, so many things there were somehow connected to the departed, that he had a panic attack. It was the kindly intervention of both the Headmaster, and the spirit of his many times grandparents, that he calmed down. Guided by both the spirits and the Headmaster, the young Potter learned to properly utilize his talents, honing them. After all, it is quite rare for a naturally talented necromancer to be born.
Harry had an unnerving reputation even among the students. Though he was kind, he spent more time among the dead rather than the living. For example, when the delegation from Beauxbatons came, he found a moment to talk to a silver-haired girl. He complimented her wand and casually mentioned that her grandmother loves her very much. Fleur was understandably quite unnerved by such a conversation starter. Her unease grew when the younger boy mentioned things only her departed grandmother could have known.