I disagree with number 3. I think that if you have an itch for no reason (other than the blanket tickling you) then it's your body testing you to see if you are asleep or not. If you move it will know that you're not asleep and hold off shutting itself down.
I wouldnt say the body is testing you, but true it will hold off shutting itself down. What i was saying was If its that constant wont go away itch, Its better to just scratch it. It always set me back further just trying to ignore somthing that is so annoying.

I dont think the body is testing you to try and make you fail. Its just going to sleep. either come with it, or stay out of its way.