If a blockchain cannot be rewritten, what happens to those coins that have its users lose their keys?

The coins just sit there unused and unclaimed (barring a brute force attack).

Some estimates are that the creator of bitcoin, Satoshi Nakamoto, holds around 1 million bitcoins. It's an estimate because all of Satoshi Nakamoto's bitcoin addresses are unknown but it's reasonable to assume the genesis block's bitcoin address belongs to Satoshi Nakamoto:


That bitcoin address remains untouched. A few people who are worried that Satoshi Nakamoto could theoretically sell off all the owned bitcoins have suggested that the Bitcoin Core code should be altered to remove all of the suspected bitcoin addresses owned by Satoshi Nakamoto to prevent a sudden sell-off.

There are also stories of people who accidentally threw away computer drives containing cryptocurrency private keys or accidentally deleted them.

As Satoshi wrote on bitcointalk.org on June 21, 2010:

"Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone."


Those coins that are in addresses the private keys to which are permanently lost will sit there and never be spent again. 


The Blockchain with its many unique features, gives so much to all users. When you start registering and getting their account's Active / Password key. It is clear that all only with simple rules:

1. Keep and keep your password in a safe place, do not lose your password, it cannot be recovered and your money will be lost or can no longer be used by anyone.

2. The second thing is in some other places / wallets giving a buck up key or nemonic code, where it can be useful if someone loses his account key / password, but it must also be understood that you also have to store it properly in a safe place so that will be useful sometime


The coin only stay there unuse nd unclaim, it become of know use to the owners that why useers must also remember the password nd key they use while registering forany blockchain or coin to avoid losses of any kind