Fadi Barbàra's Brand

1 btc is NOT equal to 1 btc

TL;DR because to date bitcoins are not fungible tokens.

How bitcoin works (basically)

Bitcoin is a decentrable system of ownership transfers. It happens that the underlying property to be transfered is considered money (losely speaking). Therefore, this property can be divided and compacted as desired. The owner demonstrates the current ownership of the coin when he decides to spend it, that is to entrust the ownership to another. To do this he solves a cryptographic problem.

There are several types of standard problems to solve in order to redeem (i.e. spend) a transaction. For example, in the simplest case, called Pay to Public Key Hash (P2PKH), the owner demonstrates knowing the private key related to the public key that gave rise to the address. It demonstrates this by producing a signature of a predetermined message: an encoding of the transaction that gave him ad interim ownership of the money.

Why is it traceable?

The on chain change of ownership of the currency is visible to anyone: the transfers are public. The only level of privacy is given by the fact that "addresses" (i.e. encoding of public keys) are used instead of people's names. The addresses act as nicknames and the system is said to be pseudo-anonymous.

Not all addresses represent public keys: as mentioned before, there are many standard problems. Some of them require knowledge of a script (Pay to Script Hash or P2SH transactions) which can obfuscate which keys are used. Still, data will be for ever stored in the blockchain data structure. Therefore data on blockchain can be mined for ever, and people will have a good understanding of where the coins come from. Note, for example, that you can rely on information outside the blockchain such as cookies, KYC related info etc.

If you want to check it for yourself, start with Sarah Meiklejohn's paper A fistful of Bitcoin and continue from there. The Meiklejohn paper is a little old today, and many things changed (also thanks to that paper), still it is a good starting point.

Traceable bitcoins aren't equal

If you can reconstruct the history of a Bitcoin, then every bitcoin is different from another. If nothing else, because of its history.

In an era of virtue signaling, polarization and high politicization like the one we are living, it is certain that someone will decide (or has decided) not to accept bitcoins that derive from "unethical" transactions. And anything can be seen as unethical: if a real communist could logically exist, he would consider any transfer of capital that does not come from the state as unethical. And so he, and all those like him, might decide not to accept bitcoin with a history that features "non-state addresses", as he might call them.

Now, obviously we are not all real communists (since they don't exist), and therefore some will start accepting "dirty" bitcoins, albeit with higher fees. For example, some communist merchants (??) will decide that "unethical bitcoins" are worth 10% less. So, if a product costs 1BTC and you only have dirty bitcoins, then you have to pay 10% more, i.e. 1.10BTC. Why not put an ethicalizing market then? I can sell you 1 ethical-BTC if you give me 1.05 unethical-BTC. it is convenient because a 5% premium is better than a 10% one.

If the example of the extreme communists does not convince you, here are some that can be considered more probable:

In all of these cases, in order to buy products or pay taxes it is necessary to go through a market like the one described above. So some bitcoins are better than others. And which are the best of all? Probably the ones with no history, i.e. those that come directly from mining rewards. But if the "new" ones are worth more, then 1btc is not equal to 1btc.