I think most of us agree that whoever is in the window seat controls the shade, but with airlines cramming more seats into planes, the windows don't always align with the seats. So the more interesting question is who controls the shade if it is between seats. I like to look out the window and sometimes the only one I can look out of is ahead of my seat aligned with the headrest ahead of me. I find it really annoying when the person ahead of me reaches behind their head to block my view, but so far, I haven't had the nerve to actually reach ahead and reopen it. This isn't really an issue with Southwest, but has happened on other airlines where you can't just choose whatever seat you like on boarding.