Himeno writes: "Even if the issuing carriers CoC says something, you're still bound by the fare rules."

Are you sure? If I buy an ordinary restricted nonrefundable AA coach domestic round-trip, the fare rules will surely sane nonrefundable. But if AA cancels a segment, there is no doubt in my mind that AA will offer a full refund to my oringal form of payment (among other options). And I believe they are required to do so precisely because their COC so provides (section "Involuntary Refunds"). In some respects surely COC does modify rights otherwise set out in fare rules. The documents interact in interesting ways -- sometimes directly contradictory, yes, but then it is a question of judgment to properly interpret the contradictions and determine the proper lawful result.