I think of it less like replacing and more like the things they like about the version of me they know are similar enough to like in me too. If he turned up too I'd hope it wouldn't be too much of a problem. I know if our world's Steve turned up I wouldn't stop being friends with this one, same thing with Bucky or T'Challa or T anyone else.
Some of the others don't really think about it. But no, they seem to just... ignore it. You might've seen Ahsoka around, or Pixie or Kurt Wagner. You could probably ask them for more details but they haven't had enough problems for it to be noticeable.