That’s not what is demanded. No one demands that the audience (users) forget what I said (the comment), much less: immediately. No one is asking for mind-erasing power or the ability to remove screenshots from other people’s client devices.

Well, that why it is an analogy; the forgetting is equivalent to erasing from someone else's storage. You have no real control over it. Other people can say they do, but you don't know that. And that is what is being demanded - right now I can already "delete" my comments and Beehaw will indicate to other instances that it was deleted, but it can't control whether they do it, and it has no way to know if they really deleted something or just hid it from public view.

Differentiating between a client and a provider becomes extra tricky when you remember everyone can start up their own instance and still be essentially just a client - and, I think this is also worth mentioning, people can create their own backends that also federate using ActivityPub, but which are not open-source, and you'll have no idea what goes on in their servers. In the bar analogy, this would be people watching a stream of the mic at home; or another place, other than a bar with the same set-up, streaming and recording what goes on in that bar.

Also, if no one is demanding that things be deleted from client devices, then logically nothing should stop someone from sharing it with other people/clients. And if you believe otherwise, then as example: what if someone posts a comment, I reply, and then they edit it to put me in a bad light? Is it an invasion of privacy for me to show what it said previously?

This is not a privacy issue; you cannot demand privacy for something you shared willingly and publicly.

Respectfully, I find it more counterproductive, and even harmful, to encourage and spread the idea that people should have any expectation of privacy regarding things they have shared publicly.