Bitcoin is trading at about $81,300, and it is staring at a ceiling made of its own recent history. A Bitfinex market report published on October 26 flagged roughly 874,000 BTC accumulated in the $81,000 to $82,500 price band — coins bought by investors who are now sitting close to breakeven. Every time Bitcoin pushes back into that zone, a large group of holders has a reason to sell: not...