Screen turns off when I move my MacBook when it is on the sleeve
It's because the sleeve has a "Magnetic snap closure with no zippers" which actually mimics the magnetic latch that's triggered while the lid of the MacBook is closed which turns off the screen. 

I've noticed this happen to me a few times in different situations when I would put my iPhone on the hand rest part of the MacBook or If i left my Adonit Jot Pro(which has a magnet to attach itself to the iPad) stylus very close to my MacBook.



You can try to reproduce the effect by taking a magnet over the marked location (at least on my non-retina MacBook Pro it happens over there, not sure if the position has been changed on Retina MBP)

EDIT - I now have a MacBook Retina, I haven't noticed this effect anymore. I'm guessing the position of the magnetic latch has been moved.