deleted by creator

Don’t we already have that in the form of PKI? (Think TLS certificates, PGP/GPG keys, SSH keys, et al)

If someone’s posts, articles, videos, interview recordings, etc. were signed with the author’s private key, then we could all verify it with their public key.

Of course, there’s a technical barrier to overcome but I imagine it would be the same with whatever Obama’s proposing here.