Stripe noted today in their blog:
When you refund a transaction, Stripe will return the entire fee. Until today, if you charged $100 and then refunded the transaction, it would still cost you $3.20—that is, 2.9% + $0.30. From now on, it will be free.
Finally! Yeay! One of my few quibbles with them is no more. It's not like it has been a big burden, but it's nice that a refund essentially undoes the transaction.
Furthermore, they won't charge you fees on a chargeback if you win the dispute. Though chargebacks happen so rarely for us now (compared to PayPal, especially!)