Here's why this encounter bothered Harry:
* Intense scrutiny: Mr. Ollivander seemed to see right through Harry, examining him with an intensity that made Harry feel uncomfortable.
* Knowing about Harry's past: Ollivander knew about Harry's connection to the "boy who lived" and the fact that his mother was a witch, despite Harry not knowing much about it himself.
* Seeing Harry's scar: Ollivander's focus on the lightning-shaped scar on Harry's forehead made him uneasy. The scar held a hidden connection to Voldemort and was a constant reminder of his past.
In short, the encounter was unsettling for Harry because it felt like Mr. Ollivander knew things about him that he didn't even know about himself. It felt like he was being watched and judged, which was especially unnerving after years of neglect and mistreatment.
However, this encounter was also crucial for Harry's journey as it marked the beginning of him discovering his true identity and magical abilities.