Honestly if it was my stand and I came upon someone in it I would think poorly about that person. Doesn't really matter, I think most people deep down know it is not right. Give a guy some space and when you need it he will too. Do you really want someone walking under your stand to get in the stand next to you where your friend is perched? What if, while you were just about to draw on a nice buck, the owner of the stand came walking up to hunt. Now if you had given him some space maybe he would spook the deer to you or not spook it at all. I know people cross paths, but if I can avoid it I will. Even if it means not sitting on the best spot on the property. Remember it doesn't take much to burn out a stand or an entire area.
This year I was setting up a stand (For My GF) in an area I had my eye on for a while. This is on private property where I have permission and so do several other hunters. I was setting up the climbing sticks when I look over 40 yards away and see a new stand setup. It wasn't there when I scouted the day before. This isn't a fun thing but as adults we have a responsibility to do what is right and safe. I broke my setup down and moved on. I setup in another spot a couple of hundred yards away.