well, that depends on your threat model. for me, an acquaintance finding out who i am talking to isn't a threat. a threat is profiling by big companies. and already by either running my own server or using a smaller paid email service, that threat is drastically reduced.

in fact this particular threat that you describe is more likely to happen at a university server where a rogue admin may use their privilege to snoop on people they want to stalk for whatever reason, as opposed to the friend that i chose because i trust them, like say the admin of the server of the local linux user group or the hackerspace that i am a member of.

in fact i am more likely to trust anyone that i know in person, simply because even if that person decides to snoop on me we can work that our in person, and the likely hood for it happening is low because it would affect our friendship. and i would guess that this is true for most people.

at some point you have to trust someone, and the closer you are to that person, the easier it will be to resolve problems.

That stalking thing also happens in personal peer networks. For the messaging app to have any relevance, you're going to want most of your peers in and once there's a few hundred people in, there's power to be abused.

University students don't get to run infrastructure of the facility, and at least in my uni, the old beard IT staff members and faculty don't really hang out with the students aside course environments or support groups, so there's a bigger gap. There's also salaries and careers in the line.

But bickering about who's trustworthy is pointless when there's trustless architectures for those situations already.