I haven’t owned any KOMs so not sure how I would feel about losing one. I don’t think I would worry about someone on a group ride - how would that individual feel if someone in the bunch of a pro race took their KOM? Would they still report it?
I once created a very short segment, but purely out of curiosity. A new bridge was being built that I cheekily rode down (brand new surface, nice incline so you can get up great speed) before it had opened and I wanted to see who else had done the same.