I was in a group for the brewfest boss in blackrock depths and then once everyone went afk, ect. i killed every mob in the bar. Then i stood on this table.
Then i moved my camera a bit, and this happened.
I know its useless, but i didnt see anything posted on the forums about it, so i might as well post it !
-EDIT
Also, if u move ur camera a bit in the red screen part, u can see the entire instance like its see through.