Frankly, reading some of these negative reviews disappointed me very much as the investors in such an incredible product do not realize how to take care of a valuable down duvet.
Down is still a living thing and should never be stored in sealed plastic as it can damage the feathers and create mold! Down feathers need air & an infrequent tumble in an industrial dryer can fluff them up tremendously, help keep the down healthy. An airing out on the windowsill or laying on garden furniture in the sun is also a great alternative! Down comforters/duvet are not made for continuous washing as that destroys the integrity of the feathers and damages your investment.
Washing should only be done in front loaders (higher spinning rpm) on delicate in a mild detergent. Drying in an industrial sized large dryer on low with Tennisballs (makes them extra fluffy). Dry cleaning only at a reputable cleaner who has experience with down
feathers! You don't want your duvet washed in the day's last chemical bath.

Comforter protectors like this one from Amazon are not made to withstand heavy spills, they are made to protect the duvet from stains (occasional light spills=drops), dust, bugs, and feathers sticking out of the original cover. A duvet protector insures that the duvet does not need to be washed as often, just zip the protector open, take off protector, wash, dry, (nothing special needs to be done), put back on the feather duvet!
The protector is also not created to hold feathers without the specially made & stitched duvet itself. To prevent feathers from shifting most duvets are squared off in squares and sewn to keep everything in place, it used to be called a quilted feather duvet. If you've ever slept under an unsecured featherbed you know how much you have to fight for good coverage as the feathers slip & slide.
If you need to wash your comforter very often due to breakfast in bed (that's me, I'm notorious spilling my coffee), small kids joining you for family time in bed or have pets who are messy (I have one of them), I suggest a down alternative blanket until the kids are older, the pet problem is resolved or you can adjust your own messiness (like me!!).

PINZON created a well crafted, tightly woven cover that should hold any strangling feathers inside while still being soft to the touch. It also helps prevent allergic reactions.

I've purchased this protector for my "extra warm" winter duvet that doesn't have loops to hold a duvet cover in place. Frankly if I'd paid attention to the description of the duvet last year, I would not have purchased it! Most of my winter duvet covers are made out of synthetics and without the loops the duvet moves around. It's a pain to make your bed, have even warmth coverage!

With the help of PINZON and a couple of hacks, I should be able to secure the duvets inside the protector and avoid the duvet slipping around. Saves me a lot of money and aggravation! While there are "clips" available to secure duvet & cover, they will mash the material of my duvet cover; if they're like pins, they would create holes as most of my winter duvet covers are made out of jerseylike synthetics.
Also, if next winter will be really arctic, I can easily add my lighter weight duvet (with ties!!) and combine the warmth & snuggle factor.

If you have a feather duvet, try PINSON to help you protect your investment, I highly recommend it!

Update 11/22/22
I just used my PINZoN protector to combine both of my down duvets - ugh"¦..never realized how heavy they would be together! Now I have ONE duvet I can slide into any of my duvet covers but best of all: it's cuddly warm but not overheating and so comfortable, I want to stay in bed. With todays energy prices going up, I know I will be snuggled up in my colder bedroom, warm under the covers.
I'm so glad I bought this protector!

This duvet protector is not classified as waterproof but I am happy to report that a wine spill by one of my guests did not reach the comforter. I'm very much relieved. And the stain came up pretty easily so the duvet protector lives to see another day.

I bought this in my quest to protect myself from my dust mite allergy, I had already dust proofed our pillow cases and mattress, but the duvet was the last thing that needed encasing. I was worried about putting something on it that made it less fluffy/luxurious. I washed this cover once before zipping up my duvet. It was still a tiny bit stiff, I may give it one more wash eventually. However it's clearly very good quality (think expensive thick 100% cotton sheets). We still use another duvet cover over it, as it's super bright white and I think it would be hard to keep that way. I actually really liked adding this to our duvet set up. It added a tiny bit of weight and warmth to the duvet, that I ended up enjoying. It's still very soft. Feels like a very high quality product that will last through many years/washings.

I can't speak to it's specific limiting of allergies. I have been feeling better but it's really hard to pick that apart from weather/cleaning/allergy meds. It has been winter the whole time I've had this and I wanted to limit dust AND pollen. However, as I said, I have been feeling better!

Bonus: boyfriend who doesn't have allergies does like it to. Other than the investment in price no real downside.

I'm so happy I bought this. I was suffering from chronic sinusitis for years. I went to an allergist and found out I am really allergic to dustmites(which live everywhere) and that I should really not be using a feather duvet. But I love my feather duvet and it was expensive so I gave this a try.

When I take the duvet out to wash them the typical debris from a feather duvet is in the cover.

Since I've gotten the necessary items for my bedding I haven't had allergy problems anywhere near as severe as I did before. It's not waterproof but it's not advertised as such. 10/10 would recommend would also buy again if anything happened to it. Great price for a product that works.

Easy to wash and dry. Looks great on the bed. Bought the king-size and it's plenty roomy. Nice zipper that hasn't warped. Great to use even without a duvet in it.