Sure, but I'm assuming most people will just air-reply. Threading doesn't add much, but always supporting kind 1111 is Alex standard practice. Makes sure someone who's client doesn't support a kind can still respond.

I tested with an single e-tag to point to the parent. But I think you are right, kind 1111 could be better. But then I am not sure if they should be displayed in chronological order, because the threading features of 1111 might make this very complicated. They would be just as regular Kind 1 threads then

It also requires kind 24 implementers to code 1111, which I am not sure it should be required. I wanted to make something very simple. 🤔