Sometimes when i just stand completely still, and i scope in on the enemies head and tap once, the bullet hit a pixel behind him and doesnt register, why does this happen, the enemy is standing still too

Hello, is there a way to block people in Valorant or keep creepy people out? My friend has had bad experiences since she would give callouts and people wouldn’t stop trying to talk to her or add her as a friend (We’re on hongkong/Philippine...