I promise I won't flame anyone... Had enough of that myself recently. I've dove with a lot of folks who don't think they've ever been narc'd. Personally I have. My first experience was because of a toilet on the deck. For whatever reason, at 130 feet, my mind simply could not process that information. Since that day, I've learned to notice the early signs and for me it's a nagging feeling to look at my guages. (more than usual). So I'm pretty familiar with my cut off point and even though you can be narc'd one day and not the next, I keep it above 170'. It doesn't mean that I don't get narc'd at less depth, just that I'm confident in my abilities to recogize what is going on and adapt. I also think conditions contribute to being narc'd. I deal with narcosis more in cold, deep, dark water than I do in cold, deep, blue water.
As far as someone bragging that they've never been narc'd, I think there's a difference between saying "I've never been narc'd" and saying "I'll never be narc'd". Just give it time...