> The sloppiness of this code is really shocking, "when the Monero client chooses mixins, it does not take into account whether the potential mixins have already been spent."

I'm not thoroughly familiar with monero's internals, so someone please correct me if I'm wrong, but I thought it was well known that this was a deliberate design decision. Previously spent amounts don't actually run a risk of being double spent as they're only used anonymization purposes, as far as I understand. So why is this is considered "sloppy"?