You end up with reputation systems, because the only thing you can know is that a public key signed a content. Whatever electronic system you will have no way to know if what it produces fits with “reality”. Just think it’s broken or hacked. You can only know that the private key owner somehow approves the content.
Only multi records of the same event from different pubkey can give a clue of authenticity as long as you are convinced they are produced from sufficient different beings (no sibyl attack).
Still a single record signed, would help. Any content without reputation will be considered highly doubtful, reputation takes work to built (cost), then a fake must be worse the risk to loose the investment. But ideal reputation systems may not be possible to obtain, they will always be some probability of being manipulated. I hope I’ll be wrong.