If you beat on a wet down bag nothing happens except breaking up the wet clumps of feathers into smaller wet clumps of feathers.
I use down sleeping bags in wet environments, such as downriver tripping, all of the time. But if the bag should become totally soaked, you are pretty much screwed. You won’t get it dry short of hanging it out in the sun for days or a large front loading drier.
Protecting a down bag from rain or from becoming soaked from immersion just isn’t that difficult. There are lots of options for waterproof dry bags, packs, and duffels that will work for that purpose. Set your tent up before you take the bag out of its waterproof enclosure and make sure that tents seams are well-sealed before you set out.
But on a longer trip in humid conditions a down bag can start to take on a certain amount of moisture from condensation. This is especially so if you use a tent with a single wall design. In my experience, a decent down bag will still retain its insulating properties even on a week long or longer trip, even when subjected to a moderate amount of condensation, however.
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I have used down bags almost exclusively as a backpacker. I do have a -20F rated synthetic that I have used for winter camping where it is calling for rain. A bit heavy though. I use my +20F down bag on most all my camping from kayaks and canoes. I have a cheap Walmart Ozark fleece rectangle that zips open like a blanket that I paid $20 for. I use it in warm weather with a microfiber sheet.
If you are going to dry your bag in the dryer with an old shoe , make sure your spouse is not home. Last time I tried it I go a lecture worse than when I seasoned my dutch oven in the oven and set off the smoke detector. 
I took a twin microfiber bed sheet folded it in half long ways and stitched the bottom and half way up the side. Works great in a fleece bag.
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Been using clean sneakers and down bags since starting canoe tripping in 1966.
The operative word is…clean.
My 19 year old grandsons white sneakers of a color now resembling a mold… no…
My wife uses something called “down bumpers” they are loud, but since the dryer is down in the basement it is not too bad. Our neighbor plays his drums in his basement… which is about as loud.
Clean didn’t enter in to it. It was the banging around. She was sure I was going to break the dryer.
I use a down bag virtually most of the time. I have a military goretex bivy that I slide it into. Also holds a self inflating pad. Cold weather, I zip it all up, other times when it’s warmer I keep it unzipped.
I prefer the wool felt dryer balls and use them for ALL my dryer loads because they fluff the clothes and linens as they tumble and they dry faster and softer. The softball sized balls are cheap (less than $10 for a package of 2 or 3 in TJ Maxx or Target). They do not make as much racket as sneakers or those hard plastic knobbed dryer balls and are not as hard on the fabric. I keep little dropper bottles of lavender, orange and almond aromatic oils on the dryer and sometimes put a tiny drop of one of them on the felt before running the load for a bit of pleasant scent.
Tennis balls are what I use.
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The wool balls are a more muffled “whump whump” than the rubber-cored balls.
I do not wash my down sleeping bags, always use a bag liner, when out in the mountains I wash myself with a towel before getting in, has not lost any noticeable loft after doing that for about 20 years, Western Mountaineer bag.
Wool retains some insulating quality when wet. Witness the early WW folks in boats they made from molds in their garages - they all wore wool.
Down and synthetic fluff like primaloft only retain warmth if they stays dry. Note the improvement in those jackets the last several years, where they finally added waterproofing to the outer shell.
In that case ( even though it doesn’t break the dryer) , wife rules.
I have three of those but they are not enough mass. Sometimes I lose one and the dog finds it and buries it way under the bed.
I just go to the laundromat. The one by me has front load washers and they can take a big heavy load and nobody complains about the sneakers in the dryer. Weekdays, its a nice place to read too.
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We are talking about wet environments, not washing machines, hand washing and commercial dryers. In the bush when a down bag gets wet you are screwed.
The only remedy I found was a cabin with a wood stove in it. I hung the bag up in the rafters and it was much better after about 8 hours.
not necessarily. I won’t go into the errors of my ways but Lake Superior entered my down bag. I wrung it out and banged on it to fluff as best I could during the last two hours of daylight over but not directly over a fire. I lived albeit not comfortably. I suspect the air mattress ( dry) underneath had a lot to do with that.
The “hydrophobic down” bags and comforters, filled with feathers treated with Nikwax or other agents that tend to repel moisture, do seem to do better in moist environments.