The FAQ explains that when exchanging currency on the weekend Revolut “apply a small mark up on the spot rate as the Forex markets are closed”.
I completely understand why you need to do this, but how about refunding any difference between the mark-up and the rate Revolut was able to achieve when the markets reopen?
At the moment, in order to avoid this mark-up, I have to estimate how much money I will spend in a foreign currency on the weekend, and do the exchange on Friday. It’s pretty annoying if I guess wrong, or forget to exchange before the markets close. I would feel a lot better about getting a “bad” rate on the weekend–and therefore better about using Revolut–if I know the difference will be refunded. (I assume you’re not actually trying to make money from this arrangement.)