Scrollback ( https://scrollback.io/scrollback https://scrollback.io/scrollback ) does, but in a different way (just two levels threading, each thread displayed

Scrollback ( https://scrollback.io/scrollback https://scrollback.io/scrollback ) does, but in a different way (just two levels threading, each thread displayed as a card). I don't think HN-like multi-level threading would work very well with chat - you expect chat messages to be chronological.