Originally Posted by mpattdu

How is it not acceptable, so long as the sleeping passenger was not denying another passenger their assigned seat? Luck of the draw (or careful planning) to end up with a row to yourself.

Anyway, only 3 additional passengers could benefit in the scenario you outlined. That would entail a middle seat passenger moving from a full row of three over to the aisle seat of slightly less empty row (assuming the sleeping passenger wants to keep the window). Not worth the FAs trouble if you ask me. If you wanted the seat you should have asked for it before the other passenger fell asleep.