Seat tilters. That's the biggest discomfort for me. The person in the seat ahead tilting back. If there was a seating section that didn't tilt, I'd take it. I'd even pay a little extra for it.
Or when, like happened to me, you get involuntarily relocated from the exit row seat you paid extra for? (Without compensation, since it was done by the flight crew during boarding and not in advance. Thanks, Singapore Airlines!)
It's fantastic, all airlines should introduce it.
The end result is the same either way for the person in front me, so I feel no guilt in using them. I also make a point to never recline my own chair.
I'm tall enough that in coach my knees make full contact with the seat in front. I just keep them that way for the first half of the flight, and the person in front of me assumes the seat recline is broken.
And if they manage to recline anyway, I make sure to hold my food or drink or reading material directly above their head while I eat, since they're pretty much in my lap anyway.