It's a long story, but I ended with a paid (discount) J fare to NRT at the end of the month instead of the expected Tango fare, which was fabulous news. However ... I need to spend a big chunk of the flight working with one of my two colleagues (who are traveling in Y), and as I recall the crew are usually none too keen with people swapping seats back and forth between J and Y. So I think I need to gift my seat to my other colleague (the lucky guy!) and spend the flight in Y. But if I do that ... should I inform the SD that in fact it's not tomh009 in that lovely J seat but his colleague, or should I just keep quiet? So sad ... a legit J fare and I end up in Y after all.