As I mentioned in the comments, I can see this going either way depending on how the question is presented. To get the "community" aspect in the question, though, I think we need to focus on how the community can interact with the participants.
- Can the community interact directly during the event?
- Can the community interact indirectly (ex. provide a counter argument, additional facts, another perspective, etc. but it needs to go through the moderator who can choose to share it or not with the participants)?
- Can the community interact after the event and get a response?
- Can the community interact in an unsanctioned way after the event to continue the discussion (ex. a third party message board, sub-reddit, etc.)
Since you are also interested in the moderation aspect, I believe we need to consider whether or not the moderators help to manage the community or the debate participants. If the moderator is only there to move the event along, provide fact checking, etc. and doesn't interact with the community, I am having a difficult time coming up with a way to make such a question on topic. In this case, the moderator as more of a referee - enforcing a set of rules for the participants and ignoring the audience - than a "moderator" in terms of building a community.
A community can exist even if they are passive and have to go elsewhere to interact. Much of the "building" is on the community though, and interaction with the "official" event isn't always easy. Think of personal blogs or popular sites that don't accept user comments. These can have a loyal following and that following can set up their own area to discuss recent posts. But, if the community wants the authors to write about a specific topic, they have to jump through the additional hoop of getting the authors to look at their unofficial gathering place.
This isn't a firm yes it's on topic or no it's not, but hopefully gives you an idea of what would make it on topic. If you can focus the question though, it can be on topic.