Gemini's text specification is kind of a subset of Markdown -- it supports three levels of headings, block quotes, bulleted (but not numbered) lists, preformatted text, and links (but not inline links).
While I'm a fan of richer text styling -- I'm often the dingus on HN being downvoted for suggesting that web fonts are not an intrinsically bad thing -- I think Gemini is mostly just fine the way it is. The thing that's kind of a blocker for me is, of all things, no way to emphasize inline text. Changing text from regular to italic/oblique carries semantic meaning. If you could mark it with _underlines_ like Markdown, for instance, it could be just like some of the other Gemini text that's described as "strictly optional for clients to do anything special with".
In the very first days of Gemini's design, I was arguing with other implementers for using a large subset of CommonMark (no raw HTML, no inline images, but pretty much everything else) as the preferred content-type to serve over Gemini. In the end, the goal of ease of implementation for client authors won out. The main arguments were that while there are Markdown parsers for many languages, most of them are narrowly aimed at converting to HTML; Markdown has known ambiguities; the line-oriented markup we ended up with was a strict improvement over Gophermaps while remaining equally simple to parse.
I also miss inline emphasis and other kinds of text-oriented typography, but the reasons gemtext omits them are fairly good.
I come to think of it, this is a client problem (specifically the client used to write the pages): gemini is natively utf8, bold and italic are present in unicode!
In general, on gemini, all "problems" are with the client and not with the protocol ;)
While I'm a fan of richer text styling -- I'm often the dingus on HN being downvoted for suggesting that web fonts are not an intrinsically bad thing -- I think Gemini is mostly just fine the way it is. The thing that's kind of a blocker for me is, of all things, no way to emphasize inline text. Changing text from regular to italic/oblique carries semantic meaning. If you could mark it with _underlines_ like Markdown, for instance, it could be just like some of the other Gemini text that's described as "strictly optional for clients to do anything special with".