> According to the rest of the discussion on this page, Visa and other payment networks refund the interchange fee to payment processors (including Stripe) on refunded transactions.

So far said that the refund fees on the brand side specifically increased or came into existence. I don't know if they did or not. I imagine though that transaction fees rising (which people do mention in the discussion) has an effect here. If you were able to make a given margin before while still allowing refund fees to be returned. Now transaction fees increase. As a PSP you can either choose to increase your processing fees or find other ways to make even. If you can achieve that by not returning fees on refunds (and make a bit more money along the way) that makes sense to me.

My main point is that rising fees in general can be a reason here even if the card brands didn't specifically add a new cost to refunds per se.