I didn't explain more because I thought the example I made was clear enough.
I organize events with the help from various people. Those events are posted in a "Global Events" section, with many other events topics, organized by others. I want these people to have moderator powers (edit, delete, etc) over their events topics, but I don't find adding every one to moderator of that board, a viable solution. That would mean that the people from Event X would have powers over the topics of Event Y and Z and I don't want that (better safe than sorry, specially on the internet).
What happens? Everyone starts bugging me to edit posts with the more updated info and whatnot. It would be avoidable if I could assign people edit and delete powers to a single topic, that way they could manage their one single topic the way they would see fit.
I said it makes sense because in my head I made a real life analogy with conversations. Topics in SMF are just that, conversations around a topic. And single topic conversations can have moderators (politics and debates) assigned to them.