I hear you, but in this case (A) there was a ton of relevant context about aria-label, and (B) HN (HackerNews) is a technical community, and on the web, "a11y"

I hear you, but in this case (A) there was a ton of relevant context about aria-label, and (B) HN (HackerNews) is a technical community, and on the web, "a11y" has been in very widespread, even mainstream usage for many years, to refer to "accessibility". Notice how "a11y" looks like lowercase "ALLY", as in ally or friend, of the differently-abled.