I like the general structure and agree that we should add an announcements channel.
I have one question: How should one deal with smaller topical groups? There is a small JuliaGeo community with a github organization maintaining a few Geoscience related packages and a low-traffic mailing list which is mostly used for announcing geo-related packages. Would this deserve its own Geoscience domain or should we create a geo tag and announcements and questions would go to the general list.