Earplugs on Airplanes

Anyone know if the following is true (from Gizmodo):

I’m fairly sure you’re not supposed to use earplug headphones on airplanes, something about permanent hearing damage

When I went to Taipei earlier this year, I had a cold and listened to my iPod (with earplug headphones), and my ears ended up being plugged the whole weekend and I had trouble hearing. I thought it was because of my cold, but maybe it was the earplugs.