When a refund may be required?
A refund request state can be triggered in some situations such as:
a) your deposit took too much time to confirm and the amount you planned to receive was sent to some order that was quicker and drained the necessary reserve required by your order, since our system does not reserve output amounts in the "CONFIRMING INPUT" state for coins that may take a lot of time to confirm and are prone to double-spending *
b) your BTCLN invoice is unpayable
c) race condition with other order(s) that took your planned amount of reserve at the same time *
d) a node/wallet responsible for payout suddenly crashed or is not responsive *
I was hoping that you would add another possibility, which I consider to be a possibility, especially for less experienced users, which relates to transactions that occur by mistake. This means, for example, that he uses the Ethereum deposit address and deposits a token on it. These incidents are often repeated, and platform systems exempt themselves from responsibility, and it is not possible to blame them for abandoning assistance to one of their customers, especially since this possibility of error is mentioned in the terms of use.
Why is it optional during the order creation?
Some users prefer not to bother providing the refund address during the address creation, since mostly it's not required. Doing this extra step for providing a refund address during the order creation is viewed as time-consuming for some people. This is however their responsibility to keep their order's URL in secret and monitor the order to avoid a scenario when someone who they shared the order ID with would take a refund on their behalf, since any refund address can be entered if it wasn't defined during the order creation process.
I expect that experienced members do not care about filling all the fields because it is always obvious that the refund address is the same address from which the deposit was made. But the matter becomes more dangerous with less experienced customers, since a large percentage of them make deposits directly from other platforms, that is, from one of the addresses of that platform and not from a personal address.