He's shy. He likes children and the only time we see him comfortable in the story is when he's walking back to his home, Scout's hand in his.
But he stabbed someone in the leg, casually, without emotion. While collecting clippings for a scrapbook. He chooses odd ways to let someone know he likes them, leaving a strange assortment of bits and pieces in the hollow of the tree. It's a distant and unusual method of communication. And he knows enough to defend the innocent from impending danger. He's uncomfortable with lights and with talking to people.
The adults in the book consistently describe Boo as "harmless" and "innocent," in spite of the event with the scissors. The children and more dramatic neighbors manufacture dire tales of his yellow teeth and propensity to eat small mammals raw, but the people in the story whom we trust the most trust Boo and believe that he, at the core, is a good person, just kind of odd.
You'll have to read the rest to discover her conclusions. And you'll have to post a comment to let us know yours.