The whole point is that they weren't spying on you. The observations of your behavior were made entirely client-side, in your browser, and never passed back to Mozilla or anybody else.

Defining that as "spying" strikes me as a big reach. It's no more spying than (say) Windows observing what programs you use most and adding shortcuts to them in your Start menu. Software adapting itself to fit the user better is a good thing, as long as it's done in a way that respects the user's privacy, which keeping the data 100% local absolutely does.

This breaks the HN guidelines. Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize.

https://news.ycombinator.com/newsguidelines.html

Edit: we've had to warn you a lot. Continuing to break the guidelines ends in bannage, so please clean up your act.