I do have a wool comforter - haven't had cause to wash it yet (and I don't recall whether it's machine washable or not. . . I should doublecheck that actually before winter) but my loose plans are to handwash it in my bathtub on a day that I can dry it outdoors. I also have some not-machine-washable wool pillows, and I've spot-washed those before with a gentle liquid detergent, and left to dry outdoors (which is good regardless for the wool whether you've washed it or not - to sun it outdoors regularly, it's said that it helps it re-fluff up too).
I do know that the wool they use it the machine washable pillows or duvets is different than the non-machine-washable ones (though I don't remember enough to tell you how in detail), such that it's less likely to felt up with the agitation of a gentle or handwash cycle in your machine. And either way, it's also different then the variety of kinds of wool that you see used for diapering too.
I'd be pretty apprehensive of putting it in the dryer at all. I'd also try to make sure to use a washing machine without a central agitator. And I'd use a gentle liquid detergent (can't remember if woolite is okay, but it likely is, I use liquid charlie's and also have kookaburra wool wash which I'd also use on my wool bedding items).
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