I've made a small extension for Safari (Mac/iOS) to highlight new Hacker News comments. I switched from Chrome two years ago and really missed my HN extension but I always assumed someone else would make one for Safari. Well, no one did so here I am. It's pretty basic for the moment.
This feature actually exists natively on alpha, email dang to turn it on for your account! :D
(It currently has some limitations your extension may not have though!)