a #nostr #relay could be programmed to analyze all the publicly available data, sort it and present a curated feed, that is personalized to the npub. such a sorting algo would NOT be centralized, because users could run their own relay. the sorting would also be done only to serve the needs of the user (not the relay). I refer to this kind of relay as a #treelay because its based on

GitHub

GitHub - baumbit/peercuration

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and the end-product is a content tree graph.