Depends... If your mother in law sees then she will think you're a bad housekeeper.... If you're having a photo shoot for better homes and gardens, they might reject the photos of your bedroom...unless you're going for the shabby chic look... Then you want it all to be wrinkled.
I've had a bedsore....the bedsore is caused from pressure at the point of the bedsore....not the wrinkle in the sheet...a bedsore can also be caused by friction between the patient and the bedclothing. And yes, it took about 2 months for it to completely heal....the bad thing about it....I have about a nickle sized scar on the back of my head from it (yes it's bald there). Probably the only thing that a wrinkle in your sheets would cause is an impression on your skin. Like when you wake up in the morning and have a long reddish scar like impression across some part of your body.
Wrinkled bedclothes can cause bed sores not just in elderly but in every one. And once you have these bed sores they are hard to heal