I've long had the sense that rate desks are sure to add taxes and fees for new segments upon xONEx reissue, but aren't likely to give credit for taxes that were originally applied to the ticket for segments no longer being flown.

Usually it's been paper tickets, the taxes and fees are effectively encrypted in the calc line, and taken one at a time aren't worth losing a lot of sleep over even if one could decrypt the line.

But I just got off the phone having changed a premium departure LHR-HKG to CDG-HKG. London was a stop and presumable attracted GBP80+ for the privilege; PAR likely won't let me fly away for free, but since no one has been screaming about it, is likely a much more modest fee. Yet the agent merely said "send $125". I had hopes for "where shall we send your check?"

BTW, the rate desk had considerable heartburn over the fact that Cathay wouldn't confirm the HKG-CMB segment, and at first weren't going to reissue the ticket (electronic, AA). They ended up (the agent said) writing it HKG-BKK, BKK-CMB OPN. Didn't bust any rules since I had the stop and segment available, but probably will cost me another $125 if I decide to in fact use a "real" asian stop.