Thank you, @eapl.me@eapl.me! No need to apologize in the introduction, all good. :-)
Section 3: I’m a bit on the fence regarding documenting the HTTP caching headers. It’s a very general HTTP thing, so there is nothing special about them for twtxt. No need for the Twtxt Specification to actually redo it. But on the other hand, a short hint could certainly help client developers and feed authors. Maybe it’s thanks to my distro’s Ngninx maintainer, but I did not configure anything for the Last-Modified and ETag headers to be included in the response, the web server just already did it automatically.
The more that I think about it while typing this reply, the more I think your recommendation suggestion is actually really great. It will definitely beneficial for client developers. In almost all client implementation cases I’d say one has to actually do something specifically in the code to send the If-Modified-Since and/or If-None-Match request headers. There is no magic that will do it automatically, as one has to combine data from the last response with the new request.
But I also came across feeds that serve zero response headers that make caching possible at all. So, an explicit recommendation enables feed authors to check their server setups. Yeah, let’s absolutely do this! :-)
Regarding section 4 about feed discovery: Yeah, non-HTTP transport protocols are an issue as they do not have User-Agent headers. How exactly do you envision the discovery_url to work, though? I wouldn’t limit the transports to HTTP(S) in the Twtxt Specification, though. It’s up to the client to decide which protocols it wants to support.
Since I currently rely on buckket’s twtxt client to fetch the feeds, I can only follow http(s):// (and file://) feeds. But in tt2 I will certainly add some gopher:// and gemini:// at some point in time.
Some time ago, @movq@www.uninformativ.de found out that some Gopher/Gemini users prefer to just get an e-mail from people following them: https://twtxt.net/twt/dikni6q So, it might not even be something to be solved as there is no problem in the first place.
Section 5 on protocol support: You’re right, announcing the different transports in the url metadata would certainly help. :-)
Section 7 on emojis: Your idea of TUI/CLI avatars is really intriguing I have to say. Maybe I will pick this up in tt2 some day. :-)