As a biographer and interviewer, I've run across many individuals who's mention of a scar evoked strong memories, long stories and sometimes emotional releases. Even today such passionate responses surprise me.
As I would meet people with or without my camera, I would question their life's experiences and there would always be at least one outstanding memory they would want to share. Once comfortable in their story telling they might reveal a childhood or more recent scar related event which usually turns out to be more emotional than even they would have realized.
Many times they would show me their scars which I would photograph. Here's one from a man I met at Venice Beach about a year ago. He told me the story of having climbed a chain link fence as a teenager and became injured. The scar is well healed but the memory of his trauma was embedded deeply where he revealed every gory detail as he rolled up his sleeve to proudly show me his badge of courage.