Is there anything to this comment beyond hollow, off-target sarcasm? The comment you're responding to seems like a legitimate question: The OP describes his horror at the increasingly common manipulation and misinformation campaigns on the Web as being part of Berners-Lee's motivation, but this solution seems to make them easier if anything, and certainly doesn't appear to make them harder.
I took that comment to say that its parent was calling for the impossible. So not off-topic.
For some people including your parent perhaps, it is axiomatic that free information implies an abundance of false information.
The construction was a little strange. "If only..." usually references an existing technology ironically. In this case I think they are saying there will never be such a tech.
The existing tech he's referring to is what we're approaching with the web as it is now (silos of centralized systems, in which information could be controlled), and the irony is that a large part of why decentralized systems (and tim's construction) are notable is to avoid such a scenario. They explicitly do not solve the problem of fake news, because they explicitly do not want to live in the world where fake news is a solved problem (because the issues that go with its solution are far worse than the problem of fake news).
The problem is that it is possible to do, and the solution to it is not something we want in general, but we're heading towards it anyways, and TBL is trying to avoid that with his machinations, and the commenter is effectively asking "how does this solve a problem that would naturally be solved with a solution we really, really don't want, and TBL is going out of his way not to solve?".
I think he's saying one way to control misinformation is by applying censorship, with the obvious implication that censorship is undesirable. You take the good with the bad, whether that means freedom of speech and some misinformation, or "correct" information and censoring any other news or view points.
One other option is to increase the cost of putting information out there. That's basically what we had pre-internet. Having gatekeepers isn't censorship but it does cut down on dissemination of fake news. But that too has its downsides.
Another option is accountability, requiring a confirmed identity to be disclosed with any posting. If people knew who was behind fake news, it would potentially be less damaging.
