> perhaps blockchains can be used to immutably timestamp events like political speeches, to create an authoritative historical record?

So it’s not "combat fake news" but rather "create an authoritative historical record of events’ timestamps". I’m not sure how the blockchain is in any way useful for the latter. I feel like we’re trying to force blockchain into every imaginable field without even thinking about it.

> consider the following efforts

Landings full of buzzwords are not "efforts". Like another commenter pointed out, it’s the whole "let’s do X, except in the cloud" thing all over again.

> perhaps content rights could be managed on a blockchain?

Ditto. "let's do content rights, except in the blockchain".