I know that. But at least that’s not really publicly listed for anyone to load from my home server in the original comment thread. And that’s beyond the server host’s control anyway; it’s completely within the server host’s control to decide to delete something properly on request or not, so choosing to not delete it is just weird.
Rather than having some control over my comment in the source thread on the source server, I now have zero control at all. That’s not a good user experience.
I don’t agree with your implication that because someone somewhere might be archiving my comment, then there’s no point in giving users a proper delete button.
There’s also a huge difference between my comment being publicly accessible in the original thread versus stored elsewhere in some archivist’s database. Obviously nobody can control the latter but that doesn’t mean there’s no point in controlling the former.