The whole point is that the client decides the presentation. If it wants to display images as inline, it will, if not, it won't.

Right, I guess the gemini browsers I tried did not display them inline.

I think Lagrange (the fanciest Gemini browser I know of) has the option to do that.

There are, but the markup is too simple and too "pure" to be useful in any meaningful way.

That's just an opinion. The reason nobody (relatively speaking) uses Markdown to author web pages is also that it's too simple to be useful.

I have 8000 pages that say it isn't: https://taoofmac.com/static/graph

It’s great for journals and people that like to tinker with a simple spec.

I wrote a similar spec for lists: https://lists.sh/spec

The renderer is crazy simple when you can figure out the type by reading the first 4 chars of each line.