“Sorry Mr. 12B, your space begins where my seat back stops, when in the reclined position.”
Yes, well, my space includes the tray table, which I should have some expectation of actually being able to use to get some work done. That is why I am particularly vigorous with my use of the tray table when the person in front of me has decided to recline their seat under inappropriate circumstances.
LOL
And those circumstances are defined by you.