pinniped

Sounds like the main problem was unruly passengers in Row 9, not the seat swap itself. Without knowledge of the Row 9 pax, I would prefer 8H over 11H, especially knowing that 8J was broken and would remain empty.

(Granted, 11H should not have assumed that he was entitled to the seat. He should have politely asked for the swap. Again, without knowledge of the Row 9 pax, I'm guessing you'd have thought "Cool...8H with an empty 8J...I'll take it.")

It reminds me of when people get mad at the guy sitting 3rd base at a 6-deck blackjack table. If he makes the wrong play, chances are roughly equal that he helped you or hurt you. Same thing here: the swap was roughly equal, and without prior knowledge the obnoxious pax could have been adjacent to 11 instead of 8.

Although we have numerous seat-swapping threads here, this one is only marginally about the swap itself.