Originally Posted by MSPeconomist

Also, remember that if multiple fares are used, the rules of the most restrictive fare apply to the entire ticket/PNR. In particular, you can't buy a RT with one way refundable and the other way nonrefundable and then get a refund for the refundable portion of the trip. However, often RTs price as two OW fares, so you could just buy two OW fares in this case.