You don't need the nodes to agree on anything. If they don't agree, they drop off the network, and form their own chain with little to no hashing power, that will stagnate and die in short order.
We have precedence on what happens if nodes/miners try to attempt a hard fork, it's called "Bitcoin cash". You need majority to agree on the rules, nodes/miners/users/exchanges all need to agree on what's Bitcoin, that's the whole point of a decentralized currency.
If a block size change caused the split into Bitcoin cash, you can only imagine what a cap change on Bitcoin available will cause, 21M cap is a lot less controversial than block sizes.
> You don't need the nodes to agree on anything. If they don't agree, they drop off the network
The miners by comparison, drop off the old BTC network making difficulty go down and others can now mine BTC.
Certainly miners can make this decision. What they can't do is force the market to value the new fork as worth anything, while they are burning energy to mine it and wasting opportunity cost of abandoning finite BTC.
No, that was the original claim. That you need the miners to agree. They are the ones that hold the computing power.
The claim I responded to says that in addition to this, you also need the majority of the "nodes", which are just computers that do no work and just forward transactions. This is incorrect, you do not need their help. It is easier if you have it, but you do not need it.
The nodes are what actually enforce the rules. If you send out a transaction with 25M coins in, nodes won't broadcast that transaction and it doesn't make it to the blockchain.
Bitcoin mining power is concentrated in China with about eight times the hash rate of number two United States, which in turn has a similar hash rate to Russia and Kazakhstan. Rounding out the top six, composing more than 90% of the total world hash rate, is Malaysia and Iran. Do you think these countries share the ideological goals of Satoshi Nakamoto's dream?
I have no doubt that a persistent 51% attack by a cartel of miners would make Bitcoin liquidity an indefinite hard zero for selected "owners" of BTC.
Also, many of the miners in other countries are also Chinese.
I don't think the Chinese miners follow any particular ideology here other than to extract as much money out of the bitcoin market as they can, though.
If a block size change caused the split into Bitcoin cash, you can only imagine what a cap change on Bitcoin available will cause, 21M cap is a lot less controversial than block sizes.