My take is reclining seats, at least the traditional ones where the seats recline back, don’t change leg room or even knee room. Seats recline back into space in front of your chest and above your knees when seated. That does make it feel more crowded and like there’s less space, for sure, but in terms of leg or knee room, there’s little if any effect.

As for how much the recline is, I think the seats go back ~3 inches, some in E+ may go back as much as 5” (I think at one point, the extra recline was marketed as an E+ benefit, but IIRC, PMUA aircraft were the same recline and it was only the newly installed E+ seats in PMCO aircraft after the merger that ever had more recline than regular economy). But IME, the recline on seats on US carriers is far less than on foreign carriers, particularly Asian carriers. I know TG and SQ in particular, I’ve seen folks able to recline back way farther than a US-based carrier recline has ever allowed. I remember one flight in particular on TG where it felt like the seat in front of me was practically in my lap the whole flight.

Many newer seats have ‘recline’ by sliding the seat forward vs. the back actually reclining - and this does take up legroom, for sure. I remember he new IOJ configuration of a ANA 777 I took in 2012, and felt like there was barely any legroom left when ‘reclined’

As for whose space it actually is, my perspective is that seats should remain upright during meal service, but otherwise, I don’t care about folks reclining, so long as they do so gently and don’t abruptly go and jolt from upright to full recline. I always take care to gently and slowly recline the seat so as not to make it a big deal and not spook the person behind me. But aside from during a meal service, I have no issues taking advantage of the recline, just like the person behind me has the full right to recline as well.

I think the actual discussion should center around whether or not a certain amount of useable legroom is actually promised. Airlines advertise pitch, not (for example) “you will have 31” of guaranteed horizontal space at knee level” (or whatever). If it is determined the airline makes such a promise, then measured evidence to the contrary could be used 1) to prove the airline does not keep the promise and 2) provide some basis for damages.

Let’s see (34-33)/34x$80 actual damages for a 1” loss at knee due to passenger in front of you reclining. Plus one million dollars punitive/emotional damages.

You’ll have to sue yourself if the loss at knee level is caused by your own actions with a seat pan that slides forward when you yourself recline.

Your experience mirrors mine, but in theory whether the hinge is above or below your knees depends on your leg length.