It would of course be the right thing to do from the sender's perspective. But is it the right thing to do from the individual miners' perspective? They have honestly mined a valid transaction, and now their pool operator is denying them the profits? Should it really be up to the pool operator at all? Should each individual miner not get to decide what to do with their share of the excess fee which they earned honestly?
I 100% agree on this aspect. As I mentioned before, I can't understand how F2Pool could make such gesture without asking participating miners for permission (unless they have it covered in Terms of Service, which I doubt).
So I think refunding it is a moral thing to do in general, but everyone entitled to that fee should make that decision themselves. You can't make good deeds with other peoples money.