There are a couple I have in mind. Like many techies, I am a huge fan of RSS for content distribution and XMPP for federated communication.
The really niche one I like is S-expressions as a data format and configuration in place of json, yaml, toml, etc.
I am a big fan of Plaintext formats, although I wish markdown had a few more features like tables.
Can you please elaborate this point? I don’t understand what you mean by “true messaging app” and why that would be a bad thing?
Are you sure this is the case? Maybe back in the day, but my understanding is this isn’t true anymore
Why is user choice a bad thing? There’s a wealth of clients that implement the features you want
This may not be an important point, but from my experience, people always blame the client and not the underlying protocol. If I face an issue with my browser, I’d likely blame the browser before I blame http.