A lot of emphasis is put on the Dursleys’ mistreatment of young Harry. We’re given signs that Harry is mistreated. He lives in a cupboard. He has meals denied to him (he’s very small). Dudley’s apparently allowed to beat on him. They don’t even let him ask questions.
…but we have no evidence that he was hit or otherwise overtly abused. The evidence is that he’s neglected a bit, the worse being his cupboard. Many children get sent to their rooms with no supper for punishment. Children have contentious relationships with their siblings/cousins. Children get hand-me-downs. Just because Harry’s treated like the red-headed stepchild doesn’t mean that he’s abused.
On the Train to Hogwarts 