The reversibility of bitcoin is no different from passing around physical dollar bills. If you want to reverse a transaction involving actual cast, you must convince the other person to give it back, or physically wrest possession of the currency from them.
Reversibility shows up when you do transactions in a bank or other third party that can reverse the transaction on its own accord. There's no theoretical reason why this can't happen with bitcoin instead - you give your BTC to a hypothetical, highly regulated bank or broker or whatever, and then the transaction is exactly as reversible as any electronic transaction using dollars. The confusion sets in when you compare Bitcoin transactions with electronic transactions using fiat currency, when they're closer in many ways to physical cash transactions in nature.
> when they're closer in many ways to physical cash transactions in nature.
I very much agree with you. This is also the right way to think about BTC exchanges -- an unregulated website that you ship cash to.
There are some subtleties around the specific nonphysical transaction mechanism of BTC that differentiate it from a cash transaction, which are sort of difficult to quantify currently because the technical and legal aspects have not been fully explored... as a hard example, imagine a BTC wallet coupled with a memorizable private key (or an effective substitute). This is essentially a cash store that cannot be confiscated, and which can be communicated verbally, i.e. within a protected (attorney-client) setting. There are some interesting implications there.
Reversibility shows up when you do transactions in a bank or other third party that can reverse the transaction on its own accord. There's no theoretical reason why this can't happen with bitcoin instead - you give your BTC to a hypothetical, highly regulated bank or broker or whatever, and then the transaction is exactly as reversible as any electronic transaction using dollars. The confusion sets in when you compare Bitcoin transactions with electronic transactions using fiat currency, when they're closer in many ways to physical cash transactions in nature.