Git histories are only as immutable as the signatures applied to them. There are plenty of git repositories that follow rebase only "linked-list" history polici

Git histories are only as immutable as the signatures applied to them. There are plenty of git repositories that follow rebase only "linked-list" history policies and require commits to be signed and through distributed consensus agree on what is the most recent commit to next commit against to keep the history a straight line. On the other side, forks happen in block chains all the time and it is an illusion that a block chain is only ever a "linked-list". It's just as much of a DAG at a technical level. The "cost" mechanics create a marketplace distinction between forks (branches in the DAG) far more than any technical distinction between them can possibly exist.