Just yesterday sitting in the Exit row I had a flight attendant ask if I was saving the middle seat for someone. I kind of gave her an odd look and said no as I am firmly in the no seat saving in premium rows club, but seems she would have been ok with it, and maybe even assisted in saving it if I had said yes.
I do engage in a bit of seat saving when traveling with my wife and son though, since Southwest hates frequent flyers and won't extend my boarding position to companions. In that instance though, a simple, "sure you can have this seat but there will be a lap toddler next to you, sound good?" has them moving on to a different row.