The recommendation engine is 100% private and on-device + it can be turned off via settings. It's novel and more experimental, but I wanted it to be available for folks to get more relevant content
For the remove duplicate posts feature, it keeps whichever is 1st in the feed (so it depends which sort method is used). It only applies for posts with the same title and from the same OP. Another experimental feature, but this has been a particular point of annoyance that I've heard from folks (i.e. the same exact post filling up a feed)
