The page fights against zooming by reducing the text size to compensate.

I can zoom in somewhat only if I press Ctrl + fast enough many times in succession, but then it is easy to overshoot.

Interesting, when I zoom in to 300% the T in TLDR is exactly 3x taller than when at 100%. Seems to be an embedded Google Doc though so the canvas does a weird recentering jerk on viewport size changes.

Zoom works until the page width is about the browser width. After that it starts fighting your zoom level.