I find it strange that we even have to talk about whether it is okay to recline your seat on a plane. The answer has always been simple. Your seat has a recline button for a reason. If you do not want the person in front of you to lean back, you should pay for a seat where that can't happen. It makes no sense to buy the cheapest ticket and then complain that you don't have the most space.

If you are someone who does not want to be reclined on, the easiest thing to do is pay for a seat where it is not an issue. The best choice is a bulkhead seat, which is the seat right behind the wall that divides cabins. No one is in front of you, so no one can recline into your space. Exit row seats also have much more legroom.

That funny idea you saw about a seat that slides forward when it reclines is real. Many premium economy cabins have these "fixed shell" seats. When you lean back, your seat moves forward inside its own shell, so the person behind you is not disturbed. You can find these seats on airlines like Japan Airlines, Air France, and China Airlines.

In the end, an airplane cabin is a shared space, but you get what you pay for. If you want more room or want to be sure no one reclines into you, you need to book a better seat. Expecting the best comfort for the lowest price just isn't realistic.