I'll be honest with MY opinion.
I do not put my seat back on flights as I think it will make the person behind me uncomfortable.
When the person in front of me does it, I think to myself how selfish and rude they are. The person in front of me has never ever asked me if it bothers me and if they did, I would never say yes it does and would grin and bear it.
I teach my girls not to push theirs back either.
I could care aless that the seat was designed to go back. It's still uncomfortable for the person behind you, IMHO.
That's my opinion and I won't be debating it.