The author mentioned they didn't like that transaction fees are not given back during refunds but unfortunately both Stripe and PayPal do the same thing. They started doing this a few years ago.
If someone buys your product for $100 and Stripe's fee is $3.20 and you issue a refund to someone you will refund the user $100 and Stripe keeps the $3.20 so that refund really cost you $3.20.
If someone buys your product for $100 and Stripe's fee is $3.20 and you issue a refund to someone you will refund the user $100 and Stripe keeps the $3.20 so that refund really cost you $3.20.