It isn't FUD when it is true. Bitcoin 30 will allow child pornography to be hosted on the bitcoin network
with no way to prevent it.
Do you need me to tell you a
harsh truth?
This is already possible.
JustThe attacker can just use Stampchain. It's easy as there are all tools
for you at
yourhis disposal. Bitcoin v30 does not change anything here.
And as @ABCbits has wrote elsewhere, it did already happen. A decade ago actually.
Then, it can be applied on all UTXOs older than N blocks, regardless of used amount. People will only go further, without taking any steps back.
I really don't believe that could really become consensus in its original form. That would confiscate all old UTXO holder's coins ...
But perhaps it can be done with a recovery mechanism, similar to Tadge Dryja's post quantum recovery mechanism where you have to show that you're able to create a TXID with your private key before you can spend an old UTXO? We're of course only talking about the UTXO set, so the data would still be in the blockchain files.
Thinking about that, this may not be a bad idea at all.