Actually does it even prevent someone from seeing it in the first place, or does it just hide the blocked person from the blocker?

At the same time, people need to understand that there’s a limit to how much (and how precisely) you can communicate in 140 characters, and that means Twitter can alert you to the headline. It’s beholden upon users to take the time to ask questions and fill in the details.

As far as certain user accounts being blocked - the SEC requires announcements are distributed publically, not universally. Anyone can watch Elon’s twitter feed in incognito mode.

The SEC doesn’t require that breaking news show up in every single Twitter feed universally. They simply require that anyone can make the effort to be able to receive the news. If that means following Elon on a separate account where you don’t harass him to the point of blocking you, that’s not exactly a major impediment.