Alternatively, it’s funny that people write comments arguing that it wasn’t targeted at Firefox users, on a post that already says that it wasn’t targeted at Firefox users :P

Specifically, everyone who’s not using Chrome and its derivates did it. Use Firefox, people.

It's linked to your account. If you view YouTube without logging in, you should have no issues. You can use the Multi-Account Containers extension to log in selectively per tab, if you need to.

Ah, so blog authors will still need to enable it manually. That's a shame.