A gravestone erodes. A memorial page depends on somebody paying the hosting bill. A message in a Bitcoin block is copied to every full node on Earth and cannot be edited or deleted by anyone, including the person who wrote it.

That property has not gone unnoticed by the grieving. Scattered through the chain are obituaries in miniature — a name, two dates, sometimes a line of scripture or a private joke. They were written by people who paid a transaction fee to say something permanent about someone who was not.

Among them is a memorial to Hal Finney, who received the first Bitcoin transaction from Satoshi Nakamoto in January 2009 and died of ALS in 2014. His last public words on the subject were the tweet "Running bitcoin". Someone put him back on the chain he helped start.