I disagree that all content on lemmy should be treated as strictly public.
Acknowledging your disagreement, it’s observable fact that it is. It’s readable to the public & open to public input. That input may be more concerned with responding to ideas (eg, as a criticism or corroboration) and presenting that to the public reader than for communicating specifically to the author of the text that inspired it. I certainly read primarily for content & ideas and respond accordingly like I’m trying to show the public something. Anyone can respond.
Comments I release to the public I treat as the public’s & not really mine. If that’s not for you, then I don’t think you’re identifying a technical limitation but a disagreement with design goals: the design of lemmy makes much sense for public discussion.
With private, direct messages, you may have a better argument.
They were complaining the blockee could write any public response even an impersonal one.
Doxxing & other issues likely already violate rules & I don’t see how that would happen, since we don’t reveal much about ourselves. I don’t see how defamation would happen without a real identity. Harassment likely wouldn’t fit the legal definition: at most, some call being incredibly annoying harassment.
I’ve seen threatening replies I didn’t report (because I consider online threats vacant hyperbole) result in bans.