Originally Posted by
docbert
The compensation is if the "air carrier places a passenger in a class lower than that for which the ticket was purchased"
In this case the OP flew in the cabin for which the ticket was purchased. No compensation was required.
I don't know what is required by law, but I will say that I got downgraded C => PE on a GPU upgraded from a Q fare and got the offered €800 plus the LH gate agent got my GPU back (it took them a while, but they did it). I volunteered, though (as in, "the offered €800"....everyone was happy that day).