These are all things you can do with HN, which has one of the simplest and most limited interfaces of all the Internet message boards. Just like with NNTP, you have to write software to do it, but it's straightforwardly doable. People have done several of them!
I guess you're thinking that one could curl down the text and then process it locally as much as one wishes, feed it to some custom reader and consume it that way. Which you're right, is possible, but not exactly within HN at that point.
And HN is the simplest use case. Tell me how I do any of the above things with messages people insist on sending via whatsapp or facebook or any such walled gardens that go out of their way to prevent interoperability?
Give me SMTP and NNTP, open standards with infinite flexibility where I own and control the experience.
