It’s only immutable if you get the whole world burning energy 24/7 to avoid a 51% attack. That solution is a little bit unreasonable, isn’t it?
Apparently there has already been 51% attacks: https://btcmanager.com/privacy-coin-firo-51-attack/
Apparently there has already been 51% attacks: https://btcmanager.com/privacy-coin-firo-51-attack/
You can keep compute systems down - i'm more interested in immutability and distributed nature than the trust issue of blockchain.
In the case of such attacks the victims will find themselves in a situation that can be described as "shadow ban" - their transactions are not accepted or accepted too late, etc.