We were recently upgraded on a flight and were placed separate from each other despite there being a couple of sets of seats together prior to the upgrades. I guess a few others got upgraded at the same time so I was unable to quickly change the selection to one next to my wife. My wife was on the window and I was on the opposite aisle a row in front of her. When boarding, I asked her row mate if she would mind switching and received a curt "no, i'd like to sit next to my partner too". And that was that. I really don't see it as an impolite request so long as you accept that no is also a reasonable response.