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Is it fair to compare the decision body responsible for forking a blockchain as 'escrow officers'? How can users of the blockchain network dare to the treat the distributed ledger as immutable as long as forking (ledger tampering) exists as a corrective measure? Who are these people and how who holds them accountable?
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First of all, it is important to distinguish between multiple things, all of which are often called 'forks'.
My view is that in a perfect world, (3) would never be necessary. We would all agree on what properties the system should have, encode those into software, and never touch those rules again. Reality is different of course, and sometimes changes to the system's rules are necessary - due to improve the technology, or to prevent against certain weaknesses or attacks. However, I do feel that cryptocurrencies (in general, as a research topic) intend to approach that goal, and are an experiment in building a system that lacks the need for human control. One of its value propositions is the prospect of creating a monetary system that is beyond control.
So how do we accomplish that? Clearly developers of node software that implements these rules have a strong influence over how it works. However, this influence is not absolute control. When you run a fully validating node, it comes with certain rules programmed in. It won't ever accept a chain of blocks that doesn't satisfy those rules. Only its operator can change that software to another version which has different rules. Developers can of course publish new versions that changes things, but they need to take into account that not everyone may update. Depending on the type of change, if significant (and not necessary large) parts of the ecosystem choose to not adopt an update, this can cause the ledger to split (where the result is 2 separate currencies, with each pre-existing coin spendable once on both sides). This risk is a strong deterrent to adopting changes, unless it is clear that those changes will be universally accepted.
So to answer your question:
Who are these people and how who holds them accountable?
You are.
Cryptocurrencies have the unique property that all of the system's rules are verifiable by everyone. By running software that implements the rules you want, you know that the system maintains those properties. Anyone who wishes to change these will at least need to convince you to change your software (this is why Bitcoin Core intentionally does not have an auto-update function, for example - it would place far too much power in whomever has control over the auto-update server).
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Is it fair to compare the decision body responsible for forking a blockchain as 'escrow officers'?
Not really. Escrow officers are generally agreed upon by all of the parties in a transaction, but there's no practical way to find someone that every blockchain user trusts.
How can users of the blockchain network dare to the treat the distributed ledger as immutable as long as forking (ledger tampering) exists as a corrective measure?
Immutable can mean two things. In a narrow technical sense, it can mean that a particular block or data structure can't be changed easily. People usually use 'immutable' in a more vague way, though. For example, the set of unspent transaction outputs in Bitcoin is not immutable, because if it was, then you wouldn't be able to send your money to someone else.
When people say that a blockchain is immutable, they usually mean that it can't be changed except through things that follow the technical rules/informal norms of the system.
Norms around how a blockchain may be changed differ between different communities. Systems with broad norms (like Ethereum) require more developer discretion than systems with narrow norms (like Bitcoin.)
If a blockchain and its community has broad norms, and you do not trust the judgement of the developers, then you can't trust the resulting blockchain, either.
Who are these people and how who holds them accountable?
It depends on the blockchain! A system based on Quorum might make decisions based on majority vote of participants. Bitcoin Core uses a do-ocracy combined with judging new contributions by the consensus of existing contributors. The Ethereum Foundation has a formal corporate identity.
It's worth noting that 'accountable' implies that there are objectively correct changes, which isn't generally true. Almost all changes are only subjectively good.
