“Last month, Mozilla made a quiet change in Firefox that caused some diehard users to revolt…”
What I don’t get, but maybe because of the lack of information I have on the topic
Exactly. That’s also the issue there. It was opt-out by default AND didn’t seemed to give enough info to the end-user about what it does, and why it would be better to keep it enabled. Most people, complain about the forced default decision without any notice, and without any appropriate info to understand if it was a decent change or not. You should only enable it, IF you understand and ablige to what it does.