[lmm]

Blockchains - that is, the communities that use them - are at least theoretically committed to immutable permanent records of everything that happened. By design, if you tried to "retroactively" edit the contents of the blockchain, you would break the whole thing. So if the blockchain hosters stick to their avowed principles and system design, they can't remove your exploit code without taking down their whole system.

Of course in reality most blockchain folk are grifters who will happily compromise their principles as soon as you credibly threaten their pocketbook - see the Ethereum DAO for the clearest example. Still, it's funny to force them to admit it.

[nuancebydefault]

In fact the blockchain cannot be broken because it is a chain. Compare it to git commits. If you would hack away one commit in the middle, the whole system would change. The other commits are comparable to any other transaction (ledger) that happened anywhere. As far as i understood, 'in blockchain' =='carved in stone' .

[lmm]

If people actually follow the rules they claim they do then yes. In practice once you ask them to put their money where their mouth is people make an exception. Again see the Ethereum DAO incident.