A.M.
J.,
I have washed my down comforter in my front loading washing machine on gentle cycle and then dried it in the dryer with 4 or 5 tennis balls to re-fluff up the down feathers.
When I don't need to wash my down comforters, I will also air them outside in bright sunshine and wind to blow the stale smell away.
I have not had a problem with feathers in the washing machine or clumping feathers once the comforter was completely dried in the dryer.
ann