Braille characters would double the horizontal resolution but halve the already limited vertical resolution, which isn’t great for something that’s intended to be displayed inline with text.

I think Teletext might be even worse. IIRC, it only has three heights for its triangles.

If you’re interested in multiline plotting with braille characters, Ian Henry’s bytemap for Janet (https://github.com/ianthehenry/bytemap) is worth a look (or my Clojure port: https://github.com/waddie/bytemap.clj).