Proposal: a standard for comment threads in Markdown files

This is the standard prose.[^abc123] Comment threads can be inserted[^def456] at any point.

Comment threads can live next to standard footnotes, too.[^aaa121] Comment threads are identified by beginning with the “🧵” emoji.

Footnotes go at the end of the document.

[^abc123]:
    🧵

    jbennett (2026-08-23T05:41:45Z)
    > This is the text written by “jbennett”.
    > The username should be determined by the current user, which could be the git user or (when absent) the local user (`whoami`).

    claude[agent] (2026-08-23T05:43:06Z)
    > This is a response on that thread. The author of this response is “claude” which is an agent. Agentic responses SHOULD be identified with the `[agent]` suffix on the username. This is important for humans.

[^aaa121]:
    This is a standard footnote. Comment threads and other footnotes do not need to be written in any particular order. The order they appear in the document usually determines the footnote number.
    Non-comment footnotes and comment-thread footnotes can easily live in the same document.

[^def456]:
    🧵

    jbennett (2026-08-23T09:09:31Z)
    > A few important notes:
    > - The timestamp should always take the same format and use the UTC “Z” time indicator.
    > - Threads can have one or more comments under them.
    > - Comment thread identifiers SHOULD be meaningless. A 3+ digit hex identifier is an easy way to ensure they don’t mean anything.