Originally Posted by
nomoreiphone
From my experience, if the aircraft suddenly becomes 3 class from 2 class and are SOLD as 3 class, then you will definitely be downgraded back to J Class at checkin - the checkin agent will pick it up in the DCS.
As for Himeno, they actually didn't swap you class at all. what is displayed on the BP may not be the actual BP. for eg. on BA they use M Class for economy class for ALL ticket type on their BP.
Rebooking for irrops normally is down in whatever booking class is required rather than necessarily keeping the original booking class. That is completely different situation to OP. I agree with others that you'd be unlucky to have a problem at check-in although of course you shouldn't bring attention to it yourself.