"Everything You Need to Know About Mastodon's New Privacy Settings" https://marrus-sh.github.io/mastodon-info/everything-you-need-to-know-about-privacy-v1.3-020170427.html
"So what changed?
...
In an attempt to fix this problem, as of the 1.3 update, Mastodon now will share your private posts with every server that follows you, regardless of whether or not that server supports privacy settings. The name of “private posts” has also changed to “followers-only” in the user interface to indicate that these posts are no longer truly private."
"Communicating to the development staff that these features are important to you is the best way to ensure they are made priorities and quickly implemented. The current project manager for Mastodon is @maloki, and you can (respectfully!) contact her with any questions you have about these new features."