My apologies, I used “reverse” and “invalidate” synonymously. Nevertheless on a public blockchain all transactions would be invalidated and that indeed is a pr

My apologies, I used “reverse” and “invalidate” synonymously. Nevertheless on a public blockchain all transactions would be invalidated and that indeed is a problem. Because everyone who received coins would have to wait again for n confirmations in order to be sure they got their money. In theory nobody should be able to add a double spend transaction to the pool but I wouldn’t bet on it. That’s what I mean with technical nightmare. You would have to make sure to properly identify all transactions. Possibly take down the system, exclude a single transaction. Make sure that the miner who will find the next block will include the right transactions. Make sure of that for the following block. I don’t see that happening with a large coordination effort, meaning: centralization. And when you come to that conclusion you should probably take a step back and rethink “why are we doing all of thatch blockchain stuff when we need to rely on a central authority?”