The search result will also include all messages related to participants who had the same nickname.You can differenciate them by comparing [JID](https://xmpp.org/extensions/xep-0029.html) and [occupant-id](https://xmpp.org/extensions/xep-0421.html).
The livechat plugin includes a Moderator Notes Application: you can write some notes, that could be associated to chat participants.Every room's admins have access to these notes, so they can edit them collaboratively.