You could achieve this with a single graph. Graphiti has a "message" EpisodeType that expects transcripts in a "<user>: <content>" format. When using this EpisodeType, Graphiti pays careful attention to "users," creating nodes for them and maintaining "fact" context for each user subgraph.

"Facts" shared across all users will also be updated universally. Alongside Graphiti's search, you'd be able to use cypher to query Neo4j to, for example, find hub nodes (aka highly-connected nodes), identifying common beliefs.

More here: https://help.getzep.com/graphiti/graphiti/adding-episodes