I never carry anything on other than my backpack, so I’ve always felt I could put my backpack in the bin because that’s my “one carryon bag”. In fact I always felt I was MORE entitled to the space in some ways because I’m taking less of it up than most other passengers.

But after reading the recent comments here I’m apparently not entitled to do this and am being selfish. So my apologies, and from now on I’ll just start putting my backpack in a rollaboard and putting that in the bin. Then I guess no one will be mad at me or ask me to move my bag under my seat. No skin off my back.