I don’t like the idea of an additional special bang. DTD, bah! Why not simply use # doctype = whatever? Also, which problem does this solve? What would clients do differently? And humans just could look at the comment or URL and see that this feed makes use of extensions – if they care. Twtxt purists would certainly hate such a new thing, too, I don’t think it helps them in any way. So I don’t see the use case for that. Can you please elaborate, @darch@neotxt.dk, what you had in mind?

My feed’s preamble starts with (links to be debatable):

# Learn more about twtxt at: https://github.com/buckket/twtxt
# This feed makes use of some extensions: https://dev.twtxt.net/

You are 💯 correct in that this would not help legacy purist clients at all as the only one that exists is broken and I maintained 😆

Let’s not solve for any ideal purism hete but for real problems that have positive outcomes to clients and users of those clients 👌