When looking at block 630873, I noticed that some addresses seem to send BTC to themselves:
Am I misunderstanding the situation, or does 1A7tWftaGHohhGcJMVkkm4zAYnF53KjRnU send large sums of BTC to itself? If that is the case, why is it beneficial?
This type of transaction is very popular amongst exchanges with hotwallet scheme. They use hotwallet (in this case the 1A7... address looks like it) to send withdrawals to clients, the change is going back to the hotwallet. Most bitcoin wallets don't allow for this behavior, creating a fresh change address every transaction.
