I would make sure the people in front of me put there seats up at least during take-off and landing. This is because I value my own safety over their compfort.

Seatback reclined makes it harder for you to get out and reach an emergency exit. Also the seat has 100% of its stability when not reclined and is more likely to break in any other position.

BTW in my home airline LH the FAs give big stress to anyone who does not comply with this, even in First Class. Most people comply anyway as it is a bad habit of Germans (in this case once it is positive) to watch if their neighbours comply with the rules or not