Comment 32 for bug 1198465

I want to say that the notion of the void payment comes from double entry accounting where you have a ledger of credits and a ledger of debits. If you want to void one or the other, you don't scratch it out from the ledger, you add a balancing entry in the other ledger saying it voids entry X from the other ledger. If you look at bills and payments as debits and credits (and it really doesn't matter which is which) this makes perfect sense.