Originally Posted by
BrisbanePE
In some cases it depends on how things are ticketed. For example QF through to UA is fine when all flights on the same reservation (ie same ticket stock) but otherwise at discretion of check-in staff at originating airport.
The QF situation is a (hopefully) unusual one. QF policy changed a few years ago to screw over anyone connecting to a non-OW carrier issued on a separate ticket by not interlining luggage. Interlining is still possible, because interlining on the same ticket still has to work, but they choose to refuse to do it otherwise.