Copperbands obviously have a very small mouth and can easily eat small feather dusters, but unless they pick at a coco worm, frill by frill, I don't see how they could possibly eat one.
And if they're well fed like were talking, what reason would they have in doing so?
You havent seen it bother it not even once?
Let me know how things arise in the future. I would really love to be able to keep both.