I know burn-in is real because I've owned a K702.
Is it true for every headphone? Of course not. Do I need an article to prove it one way or another? No. Why? For the same reason I know that my computer is right here beside me: because I can see it and (unfortunately) hear it. Prove me wrong, skeptics. I find it hilarious that so many Head-fiers are so flaky with their sense of hearing-it's truly mindblowing. I would ask: are you psyched out so easily by your other senses as well? Why is it that the sense of hearing is so wishy-washy, but the 4 other senses are generally so believable. Do you not trust your eyes when you see something? Do you not trust your hands when when you feel something? Ever farted?? Ate pizza? Nah-it's probably all 'placebo' and 'brain burn in' lol. Maybe it's hard to hear something with your head buried in the sand.
I agree however, that not every headphone will audibly change over time from burn in, as I've owned dozens, and only a few changed. But for some it was very dramatic (K702), and others-not so much. But I sure as s*** don't need a skeptic to tell me what I did or did not experience-nor would I tell anyone else what their experiences were. That's just absolutely crazy. So, burn in is real, with certain equipment. I already know it, so why would I need to believe it?