You may not have read the entire thread, so I think you misunderstood my point.

There are a lot of people whose response, upon hearing a request for an on-board swap, is "not my damn problem if you're too cheap to pay for advance seat selection".

I'm just saying that things can happen, and just because someone's asking you, doesn't mean they're cheap or stupid.

If someone asks you, you are under no obligation to move.

But every time I've asked or been asked, it's been for a similar seat, and while I've sometimes been skeptical (on the studio pods I had to think for a good 10 seconds), I've always complied. And I find most other people do too.

Even in J, don't assume that someone's a cheap last minute gate eUpgrade (or, heaven forbid, an operational upgrade). I'm pretty sure that in 2016, I had more than 5 paid J segments rebooked onto other flights due to IRROPS. Some of those I was on my own, so didn't care where I sat. But some involved companions, and I was very grateful that people agreed to move.

Heck, I remember flying SFO-YVR with rehoult last year. I booked my ticket a couple hours out because he invited me. The seat beside him was occupied. The gracious gentleman took a few seconds to think, then agreed to move. I told the SD to give him my meal priority.

I've never asked for a Y seat swap (though I have been asked), as I'm typically not in Y. I can appreciate that being asked to trade 12A for 33B may not be a very enticing offer. And I'm not sure I'd agree to that trade. But if you ask me nicely, and your seat is mostly the same as mine, I'm almost certainly going to say yes.

One time on a 763, I boarded last, took the only unoccupied J seat, and when they came around for meal orders, I realized some guy had taken my seat without asking. And I did not care one bit (though it's hard to care when you don't even notice).