> Now, determining which one is right is basically a question of whoever shouts louder... It's completely within the threat model of this situation that a nation-state might want to rewrite its identity database and deny that it ever happened.

This was a solved problem before Bitcoin: https://en.wikipedia.org/wiki/Trusted_timestamping

Now that Bitcoin exists, you don't need to trust a third party for trusted timestamping any more; you can insert hashes into an existing (stronger) blockchain instead.

I accept this is technically "blockchain" in that case, but I wouldn't really call it "blockchain technology" or "turning to blockchain" and there's no need to reinvent a new blockchain with all the risks that entail.

Take my git repository and add a rule that to be considered valid by a client an authority must have inserted the commit hash (or a child commit hash) into the Bitcoin blockchain. If an alternate branch appears, the earliest appearance wins. You get the property you're looking for, but you don't need to invent a whole new system to do it. Bitcoin (or any blockchain) isn't required; any trusted timestamp service will do instead. If you don't want to use a third party, then sure, use Bitcoin, but no need to invent anything new.

I argue that this is far better than "turning to blockchain". All the components are well understood. There is no risk in this model.