I thought the term "protected speech" usually means speech that is protected from government censorship by the 1st Amendment. But I'm not sure that has any bearing in this context since government censorship isn't involved here.

Sedition, terrorism, and advocating the overthrow of the government ARE NOT PROTECTED SPEECH

In the US, they are actually protected speech unless relating to an imminent threat. See https://en.wikipedia.org/wiki/Seditious_libel#Seditious_spee...

Just to clarify (belatedly), my point was that whether or not it's protected speech doesn't matter when we're discussing Twitter - because Twitter isn't beholden to the 1st Amendment. They are free to block speech even if it is "protected."

Michael Sherwin, the US Attorney for the District of Columbia, told the Associated Press: "All of those charges [sedition, unauthorized access, theft of federal property] are on the table... We’re not going to keep anything out of our arsenal for potential charges. We will bring the most maximum charges we can based upon the conduct." https://apnews.com/article/arrests-district-of-columbia-crim...