When I switched off fingerprinting in this browser, the font size here on Hacker News changed. I suppose it just uses the user agent to set a certain font size, or does Hacker News track based on fingerprinting?
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?