I'm personally very attached to IRC and very not interested in taking up a new platform for one specific place like this. The nature of IRC is such that it's easy to slap some easy (YMMV) solutions on top of the existing: - A bot can keep a log and send the recent backlog to new joiners - I or someone else can keep logs and provide protected access to them, contingent on agreement and conditions of IRCers Or something like that. In fact it could be that it's possible to make an IRC gateway with Matrix or whatever else -- I would have to look into it -- but as long as I'm working with my usual IRC client I don't mind connecting to something else on the back end. In the case of this project, it's true that it's important for people to be able to review and contribute, and not only on-the-fly. Some kind of collaborative / multiplayer notepad software would probably be good for this.
I like the idea of having a bot keep history. While you're at it, please put up a trivia bot. :)