AFAIK HN itself runs on Arc (http://arclanguage.org/ http://arclanguage.org/), which is implemented in Racket (formerly in PLT). Does that count? Edit: in add

AFAIK HN itself runs on Arc (http://arclanguage.org/ http://arclanguage.org/), which is implemented in Racket (formerly in PLT). Does that count? Edit: in addition, I used PLT (Racket's predecessor) for my own scientific computing needs, e.g., plotting, providing a front end to simulators written in C, etc. I didn't make the switch to Racket because it broke a lot of code and I didn't have time to rewrite everything. Limped along until Julia became a thing, and now that's what I use. And yes, could have (and did) use Python, but I really prefer writing Scheme to Python when possible.