Here’s a more nuanced approach. Once this messages is posted, it’s public. during the same day, it will be copied to a bunch of servers across the fediverse. It’s easily available to everyone who cares to look for it. After a few decades, most copies of the message will be gone, but maybe one or two will still remain tucked away somewhere. It’s still technically public, but it’s getting a bit rare. That’s ok though, because nobody cares about 30 year old online ramblings written on some archaic social media that got replaced by the New Cool Thing.

After a hundred years or so, it’s highly likely that almost every record of this conversation is permanently gone. Maybe there’s a data historian who has a personal copy of the entire fediverse. What if that one historian forgets that their Crystalline Omni-Relational Uni-Protonic Tachyon storage, containing the only copy, was in the pocket of the trousers that went into the washing machine? When they hear the spaceship keys clanging inside the washing machine, they stop the cycle, but by that point, the ‘original manuscript’ is already gone. All you have left are some references, summaries, interpretations, translations etc. Nobody knows what the original actually said, but historians just love to debate and speculate about it anyway.