You could go on for a while with different theories. Personally, I would think it's some sort of disgusting scaring. Teresa said that she was "cut open" when she became a Claymore and all the color from her hair drained away. I'd guess it's some sort of psuedo surgical procedure to put the yoma into them. If that were true, then the wound wouldn't heal properly since it was given to them while they were still human. This would also explain why the center of the chest of a claymore is never clearly seen.>>10373730
Oh wow, thank god no one reads that shit.