I had guests booked for one night. They were coming to the are to pick up a classic Lambretta. Unfortunately, the sale fell though and they cancelled my booking less than 24 hours before arrival. AirBnB refunded them part of the payment.
They didn't ask me, but I refunded them the balance, as I felt it was the right thing to do on this occasion. They were truly surprised and thanked me profusely for my generosity.
Next day I received a bunch of lovely roses and lilies.