a theory on why harry didn't turn into a obscural.
so as we know, obscural and obscurus are formed when a magical child rejects and pushes down their magic, usually as a result of abuse.
We know harry was abused by people who despised magic, and likely in an effort to get them to love him, a really young Harry would have tried to go along with the dursleys anti magic stances. He also had a soul fragment in him from one of the darkest wizards to ever live, one of the darkest forms of magic in existance, one that is known to possess unwilling victims at that. Lily's sacrifice may have prevented Tom from possessing harry, but it didn't stop the soul fragment from being implanted in his head.
He was abused, taught to hate magic, and had an extremely dark, and under normal circumstances influential, piece of magic inside him. By all accounts, this should have turned him into one but it didn't and I believe the reason he didn't was due to the horocrux in his head.
Tom Riddle aka voldemort loved magic, he believed it made him and all other wizards superior to muggles, that it gave them a right to rule. No matter how evil he was, he loved magic, even if that love was twisted it was still love, for all that he could feel it.
I believe that the fragment of Tom Riddle could influence Harry, but in response to him growing up in a house that abused him and taught him to hate magic, the horocrux instead influenced him to love magic, to prevent an obscurus from forming and destroying it.
I don't believe this was a conscious effort by the fragment, but an act of self preservation. I don't believe it was sentient like the diary, but I do believe that the horocrux might have saved the Wizarding world by stopping Harry from turning into an obscural.
