I'm gonna complain about HN though; while it may not have been intended to be mobile first, it kinda is, leading to overly wide text in comments if using a full screen browser. This is the same issue that the previous iteration of Wikipedia's design had.

You have the option to make the window more narrow, this is not a fault of the designers.

Disagree; I don't want to have to resize the window each time I switch browser tabs. Sites should work independent of the amount of real-estate my browser is taking up.

Then pray for adjustable margins to come to the web browser like in Wordpad three decades ago. That would actually be quite nice.

Maybe "Refined Hacker News" should fix this.

See: https://github.com/plibither8/refined-hacker-news

Edit: You can use the F12 debugging pane to adjust the width of a single tab without resizing the window. It's kind-of a hack, though.

Just push F12 and drag.