The CSS for HN is very terse, and aside from a mobile-specific set of rules it doesn't really do any variation.
Is it possible you had set the zoom level previously, which the browser remembers between sessions, and turning off the tracking reset the zoom to 100%? Do you have any extensions like Greasemonkey or Stylus for per-site customisation?
Is it possible you had set the zoom level previously, which the browser remembers between sessions, and turning off the tracking reset the zoom to 100%? Do you have any extensions like Greasemonkey or Stylus for per-site customisation?