They're fairly large (larger than lowercase letters in the header text, comparable to uppercase). Glad you were able to fix it since you prefer them much larger.

To be as unintrusive as possible, as per HN's general minimalist aesthetic.

Also HN was designed to be used on a PC, not mobile, around what looked good enough to pg in the early 2000s.

I just zoom in on mobile if I really want to vote on something.

I prefer that to the idea of a “mobile-first” site overhaul like much of the web has done. In nearly every case those efforts seem to make things worse.