The least you could do is acknowledge to the person behind you that you're about to do it. You're acting as if you're being told to file a permit. On the contrary, it's pretty common courtesy.

I've been flying for the last 15 years regularly and never once witnessed someone forewarning the passenger behind they were clear to recline their chair.

Because you could injure me, or at least cause pain and discomfort when you slam your seat into my knees.

I am reclining my seat a few inches, not swinging a door open. Claiming you could get injured from that is ridiculous unless you blatantly push your knees up against the seat in front of you. Sit upright with your butt all the way in the seat and you won't have this problem when others decide to recline which is within their rights.

I can't reply to your latest comment, presumably to some stupid pander-y HN ethics rule, but I've seen plenty of people who warn/ask the person behind them that they're going to recline. It's simple courtesy. To be honest, the fact that this doesn't even process with you makes you sound awful to deal with in any sort of transaction.