1. I agree that "good technique and stealth trumps...paranoia...." A careful approach to a feeding trout, IMO, is helpful.
2. I also believe that muted colors of clothing help and are a part of being stealthy and make a fly-fisherman less obvious to trout.
3. I am not sure about whether a brightly colored fly line frightens fish, but in the interest of stealth, I have always favored rather muted colors of fly line, too. Perhaps these help to compensate for my mediocre casting ability.
4. I have just begun using a wading staff the past couple of years. Mine is not rubber tipped. There have been a few times that I do believe the tapping of the staff put down fish I got too close to, but I can't really prove that. I do know this: Without a wading staff, I could no longer fish some of the places that I fished pretty thoughtlessly as a younger fly-fisherman.
(My staff is not a Folstaff [I don't know what it is]; it was a gift from my son for Christmas and has turned out to be about the best gift he ever came up with for me.)