Regarding the point about filter bubbling in DuckDuckGo: My guess would be that it's not a trivial problem for them to undo the filter bubbling that their searc

Regarding the point about filter bubbling in DuckDuckGo: My guess would be that it's not a trivial problem for them to undo the filter bubbling that their search providers are doing. But, I think if three people were to hit the "refresh" button 10 times on the same query, then the variation seen by one single person is probably similar to the variation seen across different people running the same query.