Medium compression for short periods of time is *not* a problem.
Long term compression is not advisable.
Fluffing is mostly worthless in the short term of re-lofting, and extreme fluffing immediately after decompression can be detrimental.
Here's the procedure I follow, and have advised my customers to follow, based on building and using super high fill power down sleep systems for years:
Store loosely, lightly folded, or in a large loose bag, ventilated.
Pack ideally in the bottom of your pack, inside a liner or preferably a kitchen or compactor garbage bag. This should be the first item in your pack. On top of that (inside the liner/garbage bag) put extra clothes, insulative gear, etc, that needs protection from moisture. Twist the top of the liner loosely, fold over to lightly seal, and lightly compress down into pack. Pack other items efficiently, based on weight and needed access on top of the bag of clothes and bag/quilt.
What this packing method allows, is a safe, secure from moisture, minimally compressed bag/quilt, that will compress as needed to accommodate other gear, yet expand to make for an efficiently packed, and easy to carry load. You wont have empty space in your pack, and you can compress as needed to make more room. Although if the quilt/bag area is taking up less than about 1/4 of your pack space I'd recommend considering a larger pack or reducing gear bulk otherwise, for longer term use.
Once at camp, I set up my shelter, inflate or roll out my pad, and then lay out my quilt on said pad. Extremely high fill power premium quality down (800fp or higher) can take quite a long time to completely re-loft. Excessively violent "fluffing" immediately after heavy compression can break the hairs off individual down clusters as they're tightly interlocked, and cause premature breakdown of the down. After you allow the down to decompress of it's own volition for a reasonable time, light fluffing will be beneficial to evenly distribute the clusters, but I don't recommend it until heavy re-loft is achieved.
The higher quality the down, and the heavier the compression, the longer re-loft will take. 100% re-loft can take hours(a few, not dozens) in the worst cases.
Another concern worth mentioning with down gear, is that in long term sustained use, moisture removal and cleaning become major factors in maintaining loft. Venting your quilt in the early hours after waking while packing up and cooking is extremely important, and washing or fluffing on extreme length (thru hikes) trips would be essential also.