Originally Posted by
eigenvector
OK, I'll bite. If you're re-routed such that there is not only no disruption to your travel plans, but you actually arrive sooner, what exactly are you expecting to be compensated for?
The airline's obligation is transport you from your booked departure point to your booked destination, at a certain time and in a certain class of service. Only if they cannot deliver this are they obliged to compensate you.
When they are asking for volunteers to give up their seat and offering the pre-defined compensation as part of that offer and you accept, IMO you are agreeing to that offer of removing yourself from that flight. If it turns out that you were just connecting via that flight and they can actually get you to your final destination at the same time or even sooner has no bearing on what you just agreed to. AC needed that seat to avoid IDB and you helped them by offering yours based on their current offer being worth it to you.