If you're worried about another player digging hard into your strings, then you're at a low tolerance level - not that it's bad. Like others, I was expecting him to either drop, scratch, dent the guitar at minimum. I've seen my friends do much worse, which is why I don't generally don't borrow my guitars for people to play - only very close friends. They can play the hell out of the strings and make the guitar wail for all I care - it's an instrument made to be played. The strings? I'm gonna change it anyway sooner or later - so I wouldn't be bothered by it.