What? The seat pivots below knee level by definition, unless you've found a plane where the base of the seat slopes down from the back to the front.

(Since the seat is level or slopes slightly upward from back to front then the pivot point is at the back of the base of the seat. Since the legs are sitting on - i.e. above - the seat, then the knees have to be above the pivot point and reclining does indeed remove leg space.)

Disclaimer: I'm over 6' with long femurs and have had exactly this situation happen to me on a flight. When the person in front of me reclines my legs do not fit in the remaining space, even if I'm sitting all the way back in my seat.

I understand the economic rationale airlines have for separate seat classes, but at the same time that rationale irritates me because I end up having to pay more for something that is entirely out of my control (genetics).

Same for me. On Southwest, my knees fit exactly (slightly touching) without the person infront of me reclining. Luckily I'm fairly wiry and usually angle my butt to the left of the chair, and knees on the right (or vice versa). Or I can put my feet and shins under the seat infront of me.

But a normal "feet on ground" sitting position doesn't work if someone infront of me reclines their seat.

Not by definition. Most people don't sit precisely with a 90 degree angle and instead extend their legs into the space under the seat in front of them.

If your bag is taking up all of that space, you are doing it wrong.

and the funny part is someone shorter but heavier than you pay same price as you though economically he cost airline in fuel more than you, so if we wanna be fair we should be charged per kilo of live with, same as with baggage, i am fine with smaller and lighter people paying less than me, i am not fine with someone voluntarily living unhealthy and reclining seat paying same as me

I'm under 5'7", I'll trade you your genetic shortcomings with mine, especially with the ladies;)