It happens, and it is difficult to stop once it gets started.
Boredom sets in, the muffs get wet from drinking, then they go to the feeder and bits of feed stick to the muffs. Other chickens see the feed, and before you know it they discover that feather eating is fun. When birds are given plenty of room to roam, especially free range most of the day, it seldom happens, at least here. The worst time seems to be when the breeders are locked up in relatively small pens with nothing much to do. This just adds another challenge to Ameraucana husbandry.