Okay folks, I’ve spent all day on this today, and I think its in “good enough”™ shape to share:

Twtxt v2:

• Specification: https://docs.mills.io/uJXuisaYTRWYDrl8A2jADg?both
  
• implementation: https://gist.mills.io/prologic/afdec15443da4d7aa898f383f171ec1b