Does it even matter if they know? The private content is supposed to be invisible to them anyway. The fact that they don't know it exists would make it more invisible.
Also, some platforms, like Mastodon, have actually adopted some privacy. For example, they added "followers only" posts that only their followers can see. If they are aware of Mastodon's "followers only" posts, then they already understand the basic concept of limited distribution.
At least by German law, hubmins can be held liable for what’s happening on the pubstream because it’s happening on their “website”, and so they’re responsible for it. And remember that most public Hubzilla hubs and the two biggest ones are German.
That's true. We are protected by Section 230 of the Communications Decency Act and the Digit Millennium Copyright Act (DMCA) and the common law legal concept that you cannot be held liable for someone else's actions.
Other countries may not provide the same protections.
On Hubzilla, there is a way to make the public stream available and only show posts from that server. But most Hubzilla admins never turn it on and probably don't know it exists.
As an administrator, the only time you would want to turn on the public stream is if you are a public hub and accept new signups. It makes it easier for administrators and moderators to moderate the public content on their own server since they can see all public posts in one place. If someone is posting illegal content or spam, a moderator can see it, and remove it (and perhaps the user too).
But private instances don't need this since everyone on the server is trusted.
There are concerns that your publicly posted information would scooped up by bots that scrap up public information on the web. Or more specifically, be used by Meta to build a profile on you, which it already does even if you don't federate with Threads.
People who are concerned about this usually choose not to federate with Threads, but they also would need to block bots and Meta specifically to fully be protected.
Others don't share their concerns as much, or are more selective about what they post publicly. Some platforms allow you to post privately, for example, and unless you are communicating with someone on Threads, Threads would never see it even if you were federated with Threads.
@Comment105 Commercial interests and propaganda will come to the fediverse. The propaganda is already here if you know where to look.
The biggest strength of the fediverse is that administrators and users have control over what they consume. They are not force-fed information from third-parties without their consent.
So, companies and politicians are going to show up on the fediverse. But you don't have to follow them.