I don't think I've knowingly punched down.
Edit: anyway noted. I'll try to be more American (in the old sense; I'm not sure being Trumpian would work well here!)
HN doesn’t really distinguish between “punching down” and “punching up”, and prefers to avoid “punching” at all.
The guiding principle to keep top of mind is “intellectual curiosity”. There’s a place for an intellectually curious discussion about the history and present day meaning of the word “shibboleth”, and the way you commented brings that to a screeching halt. And even if someone else seems to be acting like a bit of a jerk in the comments, it doesn’t make it OK to do it too.
But as you say, you’ll try to do better which is great.