So, the correct answer here would've been that Viaweb--Graham's company that later became Yahoo! Store--was done in Common Lisp. I'm not really aware of any other example of Common Lisp in a real commercial setting other than Mirai (which I think is dead nowadays anyway).

Graham later made Arc, the language in which HN is written. To the best of my knowledge Arc's only major project is in fact Hacker News.

So, essentially, yes, you're correct.