Interesting idea for a Nostr client: parental controlled feed and a locked-down child's client. Secondary client only queries and actively filters based on endorsement of a primary npub. As loose as "needs a signature from an endorsed npub" to as tight as "only notes specifically endorsed," and this could also be per note type. This could also be set up for chat in the first style filter. This would be great for a more free and open kids-mode in which we could even share and subscribe to each other's kids content. Chat, games, video/audio/media, etc. Very interesting idea!