I'm glad that this thread exists as I've been wanting to get this on FT for a while.
This was about 7 months ago on an hour long flight TPA-ATL, MD-90 (I'm sure you know the airline by now - there's a good thread in that airline's forum about snarky people but this is a window shade thing so it goes in the window shade thread).
I was in an A seat (window, left wing) and shortly after takeoff I noticed a hand coming in between my seat and the wall. The lady behind me pulled my window shade down. And this wasn't a case where my seatback was right over the window (where technically either row could control), my shoulder was where her hand ended up pulling the shade down. She stuck her hand in between my seat and the wall.
I was pretty appalled that someone would do that. The lady didn't do anything else, I didn't say anything, and I re-opened the shade sometime when the flight was descending. It was a mid-afternoon flight and was a nice day outside. I don't understand however how the row in front of you having their window shade open would be such a disturbance...