I agree. I said I have never seen any proof. It was just a warning of things you might hear. When I was doing TDR training in my office I had a couple hundred foot spool of IBM type 1 cable hooked up and it worked fine (just trying to get some length out there). I also had "baseband" cables coiled on top of fluorescent troffers, tywrapped to the feeder going to the elevator and every other thing I had heard legends about. The stuff just ran.
OTOH I could show you a kink in a CAT 5, every connector and a nail through it, even one that didn't pierce any pair insulation, showed up like a sore thumb. An overhand knot is pretty ugly too.
If you were sloppy doing your terminations it was almost as bad as the nail.
We were still going pretty slow in those days so the LANs still ran fine with all of these things but these days with gigabit over copper you may not do as well. The effect will usually just be the network slowing down and everything may still "work" but your LAN administrator will be tracking it down eventually if they are earning their pay.
