It's REALLY IMPORTANT to get the word out that nothing on #Mastodon / #Fediverse is truly private. People should not say things here that they wouldn't want the whole world to be able to see.
(And IMO this is a huge problem with the platform)
Mastodon lets you mark your expected level of privacy, but then it completely relies on good faith cooperation of others to respect that privacy.
I'm often really troubled because I know many people don't understand this, and they don't realize they're exposing themselves as they are.