Join Date: May 2006
Location: New York, London, Sydney
Programs: United GS/2MM, DL*P, VS*G, AA*EXP, Avis CHM, Hertz Platinum, Sixt*D, HH*D, HGP*P, Starwood*P
Posts: 9,877
Yes, certain fares actually have change fees. Usually buy ups can get change fees waived. And if you booked mixed rules, the more restrictive apply to the entire itinerary, so no point in most cases.
n.b. that if you make changes after ticketing to either segment it will reprice the entire itinerary based on fares available at that time. So advisable not to try to get cute.
It should be noted that this can possibly be mitigated with .com buy-up offers, but no guarantees that they exist or are attractive, let alone reflective of the theoretical one-segment buy-up price.