Also, most of the time icons should instead fall back to nothing (and should be hidden from screen readers). The main exception that one will observe in reality is a toolbar of icons only with no labels; it’s well understood in usability circles that that’s a dangerous pattern at best—text labels and icon-and-text labels both almost always simply work better.

I deem the ligature approach bad because it encourages leaving something in the document and accessibility tree that shouldn’t be there, and most commonly in a non-semantic way (e.g. a send button might end up showing something like “paper airplane”, which is terrible, or with this specific font, “Learn more →” might become “Learn more arrow_right_alt”), or with semantics that you’ll definitely break at some point (e.g. report_problem is , but if you use that for an alert icon it’ll mislead anyone that ends up reading report_problem; in short, any new semantics you desire for an icon, you need to create a new ligature for it if the user can possibly ever be exposed to it).