@Josh - The real difficulty here is chasing the network effect. Marketers simply shrug and go wherever the network effect has manifested the greatest collection of users. If were were doing that, it would just be Discord probably. In any case, it would involve a proprietary, corporate product hosted on someone else's servers. Not at all DIY.
But if we choose a different format and try to stick with FOSS (free, open source) solutions to reflect our development ethics, we won't get that network effect, unless we generate it ourselves somehow. FOSS solutions just aren't where most users hang out.
Email is currently one of the best "happy mediums" (probably better characterized as vaguely tolerated mediums 9_9 ) where you can have both the network effect and an open standard with self-hosted and open source software. Almost everyone online in the world, whether by smartphone or computer, has at least one email address. That's as big as you're going to get in terms of mass adoption.
I'm totally open to branching ThinkTank operations out into another platform and/or renaming it, and willing to help if enough people want that. I just want to caution your investment in momentum for these initiatives in the case that what you're really chasing is the network effect, rather than simply an interface/UX experience.