Web UI font does not have symbol for ⁻ (superscript minus)

[septatrix]

They are display as missing chars instead

[sharkdp]

It seems to work fine for me?

[septatrix]

Likely because your fallback font for monospace has that font available. For me this happens on Chrome/Android whereas on my desktop the glyph is displayed because "Noto Sans Mono" has it. In the Firefox and Chrome devtools it even shows that Noto Sans Mono provides one glyph when it includes a superscript minus. You can also check on Google fonts that Fira Mono does not provide the superscript minus glyph. Adding another fallback is likely sufficient as a workaround (though I also raised this issue upstream: mozilla/Fira#253)