Occasionally I find my duvet like this in the morning, but it fixes itself when I make the bed. Only way I could see this being an issue is through using duvet covers which are incorrectly sized, or not making the bed (properly) before getting back in.

I wonder if this is a case of people using duvets but having not been shown how to make a bed with one… For the benefit of the uninitiated, stand at the foot of the bed, grab the bottom corners of the duvet and hold them wide apart. Lift up to shoulder height then use a quick downward motion - the top of the duvet should flick out like a whip. This will push the duvet back into the top corners of the cover and redistribute any loose filling which may have migrated down through the night.

Also never seen ties in a duvet - seems pretty pointless to me.