I'm not so expert about ecash, so I don't know which data is included in that qr/string. But if there is a tmestamp it can lie or be wong for various reasons. So how it can be a proof? Please explain or fuck of me.
I have to read the fucking manual.
Discussion
You might have misunderstood. I meant that ecash sat can be used as a postage stamp.
Relays receiving the stamp can verify it is a real sat by redeeming the ecash stamp at the mint for LN sat, and then forward the message. 
Ok took it, So one sat for relay for message. That's becoming expensive. I value privacy and freedom too, but not so rich. A feature like that is for very important messages.
Maybe spending 90 cents a month shouldn't be too expensive?
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