@sorenpeter@darch.dk I like this idea. Just for fun, I’m using a variant in this twt. (Also because I’m curious how it non-hash subjects appear in jenny and yarn.)

URLs can contain commas so I suggest a different character to separate the url from the date. Is this twt I’ve used space (also after “replyto”, for symmetry).

I think this solves:

• Changing feed identities: although @mckinley@twtxt.net points out URLs can change, I think this syntax should be okay as long as the feed at that URL can be fetched, and as long as the current canonical URL for the feed lists this one as an alternate.
  
• editing, if you don’t care about message integrity
  
• finding the root of a thread, if you’re not following the author
  

An optional hash could be added if message integrity is desired. (E.g. if you don’t trust the feed author not to make a misleading edit.) Other recent suggestions about how to deal with edits and hashes might be applicable then.

People publishing multiple twts per second should include sub-second precision in their timestamps. As you suggested, the timestamp could just be copied verbatim.