Use-case specific.
That's better as it allows easier filtering for everybody -- and if you want to display everything (for whatever reason) in your client just add a new kind to you REQs.
Discussion
isn't that redefining kind-1 from nip01 from a 'text-note' to a 'social media broadcast message or reply'?
nip01 defines kind1 as: "**text note**: the `content` is set to the **plaintext** content of a note (anything the user wants to say)."