I can somehow understand that he didn't save note priv key, note public address, and letter of guarantee, but I don't believe he can't remember how much coins he donated, he can just check pervious transactions in his wallet.
You wouldn't be able to tell the selected donation % just by looking at the previous transactions in the wallet. The deposited amount appears the same, but depending on how much you chose to donate the real Note balance will be slightly lower. If you didn't save the LoG and can't check the balance with the Note private key, then you have no way to know for sure what it is.
3. Treat Whirlwind as a network and respect the rules, in this case we will not be able to help in any way and the user would lose access to his funds assuming it's true that indeed he lost the private key
That also means that you should accept any loses in case someone finds a flaw and abuses your system, this is a double edged sword.
Making everything more decentralized sooner would eliminate the need to even talk about this issues.
If someone finds a flaw and abuses the system we would take responsibility for it, it wouldn't be fair otherwise. On the bright side we are convinced this is impossible with the current setup so we are more than happy to respect the rules.
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Your deposit isn't considered valid by the system because it's under the minimum amount so your funds will be sent back automatically to the address you used to deposit.
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Please contact our support by e-mail with all the details about your situation and we will see what can be done about it.