First I want to say, BEAUTIFUL. I love feathers and hope to be able to make them that way some day.
Second, unless you micro stipple with metallic thread, I don't think you can quilt so much it makes a stiff quilt. Obviously when there is more thread than fabric, it will get stiff by virtue of the thread tension. I put some practice fabric on my long arm and scribbled all over it, then I changed colors and tried again on the same fabric. It has body but it isn't stiff (the dog likes it). I think because there are some luxuriously soft fabrics out there people assume every thing should be that way. After all, we are working with cotton fabrics and lots of seams.