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Description
when you try to send to some place you've already sent, perhaps there should be a polite "You've already sent X btc to this destination in TXN y on date Z. Do you want to continue?" which should help people avoid some of the incidents they've had with double paying.
Doubling payments is an actual mistake that people make which could be dampened by a polite confirmation, one which could be disabled with a don't tell me again, that it also provides a hook to educate people about the consequences, both for themselves and for others, is just a bonus. The education matters, considering response I've had to bip32 public chains has been "why does it matter, I know who I'm paying already". :)
Moved from bitcoin/bitcoin#3266.