Quote from: Dabs on Today at 12:58:57 AM

A double spend has never happened because it is simply not possible. Only one transaction or block made it through, there was a reorg, or something, but it was not spent twice.

The inability of someone to double-spend inputs is due to blockchain technology, not due to PoW, or Proof of whatever.

There have been many double-spends with unconfirmed transactions, in fact, RBF is a feature of bitcoin that allows users to double spend unconfirmed transactions. There have also been a handful number of double-spend transactions when there is a reorg, but this was due to the randomness of the timing of finding blocks, and that it just so happened that two miners found a block at the same height at approximately the same time that just so happened to include competing transactions.

I would argue that PoS blockchains have not seen as many double spends resulting from reorgs because 1) they see lower transaction volume, and 2) it is more difficult to get a double-spend transaction of an unconfirmed transaction to propagate throughout the network.