Hi! I found this topic when I was trying to find an answer to my own issue about shadow corners on my TV.
I just recently bought a Samsung UE55JS8005 55" flat smart tv and directly noticed transparent shadow corners on the screen.Most noticable on bright backgrounds. I have tried different hookups and settings but the transparent border is always there. Would be interesting to know if it's a fault or if all models are like this.
Just as Steve, I have a hard time getting this out of my head and it's bugging me like hell.