My most hated audiophile-related misconceptions have to do with the wild claims some people on these sorts of forums make about the sonic artifacts and differences in equipment that they swear up and down that they can hear. All sorts of dubious "facts" and guff get spread around as a result, and new members look at that and accept it because it's popular consensus, or else judge the hobby based on the intensity of the often circular arguments that repeatedly erupt about burn in or cables. They often conclude that they need to spend a bunch of money on stuff they probably don't need or, worse yet, they take up sides in these arguments just to fit in and thus keep the cycle going.
You see, some audiophiles (certainly not all) feel that their ability to enjoy audio at a deeper level than most people (which is truly a gift, don't get me wrong) makes them special and superior. It builds them up inside. That can eventually go to anyone's head and morph into all sorts of ridiculousness. People can convince themselves of nearly anything if it stokes their egos, especially if it bigs them up or they've sunk money into it. But the fact that I rarely see anyone interested in trying to prove these claims to themselves empirically tells me that, more likely than not, they know deep down there's a very real possibility they're winding themselves up and they don't want to be humbled to the fact or have to admit that they just wasted their money.
So they hide behind their jargon. They collect among like-minded individuals and reinforce their beliefs. And, though it's not really that common on Head-Fi, nevertheless sometimes they react with hostility toward anybody who challenges their claims.
There's a quote in my signature about this. It's based on my own experience, when I finally came down off my high horse and used the ABX comparator in Foobar. My transparency point for Lame MP3 is V0, which is quite high. But that's with a specially-selected killer sample. Realistically V1, and possibly even V2, would be fine. For AAC it's far lower, at around 160kbps. I used to think things like, "I can tell the difference. Listen to those reverb trails!" You'll be shocked what you can't hear when it's your cold, dispassionate computer that's keeping tally. And you'll be happy for it because you'll gain a much truer and more realistic sense of not just your own limitations (which is most important), but of the realistic limitations of any human.
And, just between you and me, you'll also save a boatload of money, time, and worrying about "What would happen if I upgraded x?" or "Would the midrange sound fuller if I encoded in lossless?".
So take what I've said as you will. Flame or agree as you see fit. I don't spend near as much time on Head-Fi these days because I'm often too busy with other stuff. But I'll say this much. I haven't got a clue who made the cables in my headphones, what chip is in my DAC, or what production run my DT880 came from (it's got the new strain relief as opposed to the original one that Beyerdynamic now only uses on the T-series phones, so of course it sounds different!). When I slap my cans on my head and put on some Genesis or the LSO, all I care about is kicking back and enjoying the music.
Because that's ultimately what it should be about.