There have been many that have converted/used the down out of a comforter to make an underquilt. It is a source for down that many use. I don't have any references, but have seen it pop up quite a few times on the forums.
"We do not go to the green woods and crystal waters to rough it, we go to smooth it."- G. W. Sears
My forum name is Fish<><; I'm in the navy; and I hate sleeping on the ground. If I didn't need ground to walk on or measure resistance to, I think I could happily give it up.