It's interesting to see the comparison with the Bluesky collaborative ranking tools. This is a critical feature of decentralized social media: block lists, promote lists, etc. Same with adblockers... domain reputation is everything. uBlock Origin is only as good as its block lists. It would be amazing if Kagi to published these kinds of lists.
It would be something like a Private Tracker: it's a database curated by and for a defined, trusted population. In this case, people who care enough about search quality to pay for Kagi. Kagi would need to be very thoughtful about how to receive trusted feedback from users without reducing privacy. Privacy Pass might be a valuable foundation for this.
Lets see if I can state this as clear user stories...
As a Kagi Subscriber, I want Kagi's high-quality signals about publisher quality & relevance available on other platforms. When Kagi thinks a domain is used for spam or other malfeasance, I want my adblocker to block that domain. When Kagi thinks a user on a decentralized social media platform is fake account, spammer, or otherwise fraudulent, I want that user to be automatically blocked from my feeds on that platform.
As a Kagi Subscriber and decentralized social media user, I am willing to share my personal moderation decisions pseudonymously with Kagi in return for access to blocker feeds/moderation lists. I don't want Kagi to build a database of my social media behavior explicitly tied to my account, but I'm comfortable sending a stream of block/unfollow/report events tied to a stable ID that is not otherwise linked to my Kagi account. I expect that Kagi will use this identifying information exclusively to prevent abuse of the reporting service.
As a Kagi Subscriber, I want the ability to search social media at scale, including the long tail of decentralized social media instances. I expect these searches to be ranked based on high-quality signals. Users who share links to low-reputation domains or are frequently blocked by other Kagi users should be downranked.