A few days ago I wrote about moderator selection in online communities, and somebody asked in a comment which is a better approach, Stack Exchange's centralized control or Reddit's anarchy, where the founder of a subreddit is in charge and communities can have whatever rules they want about content and moderator selection. I responded:
I hope we're drawing on the best of both and avoiding the worst of both. On our network we have a community-proposal mechanism, which is much lighter-weight than Stack Exchange's. (Stack Exchange now makes it very difficult to create a community, which fits with both their business model and the fact that they've got 170 of them already.) On Codidact, we'll create a community if -- hand-waving ahead -- there's "enough" interest. "Enough" is a fuzzy mix of number of people, people's specific interests (e.g. if nobody's prepared to answer questions that'd be a problem), and level of enthusiasm. The Judaism community had several enthusiastic people within hours of being proposed; we launched that in a few days. A proposal for role-playing games feels like it ought to have support but people aren't participating much in the discussion so we don't know if we should create it or wait. And, of course, we're new to this and learning as we go.
The reason we have a proposal process and don't just say that anybody can do anything like on Reddit is that we want to support both individual communities and our network of communities. If a proposal would have large overlap with an existing community or another proposal, for example, we want the folks involved to work with each other to figure out how to avoid confusing people. There's nothing wrong with some overlap (and I'd say it's pretty much inevitable anyway), but, for example, while launching our (new) math community we got a proposal for a math-and-physics community, and we suggested that the latter be reworked as just physics, or as natural sciences if the person wanted a broader scope.
We expect communities to have different norms -- about what is expected of questions, about what sourcing or support is expected for answers, about level of chattiness in comments, about how actively people should edit, and so on. Stack Exchange has these variations too, though they might not admit it. From what I've seen, Reddit has even more variation. We have some baseline requirements of all communities, we give moderators broad authority to manage their communities, and we have an escalation path for anybody who objects to an action by moderators or staff. I can't tell if Reddit has any sort of meaningful escalation or review; Stack Exchange's is a joke (they'll set aside their policies when it suits them). We're still at the draft stage, but we intend to give the community a real voice here. We always want the first step in any disagreement to be discussion, working together to find a solution.
(There's probably more I could say but I must run now.)
Edit: somewhat related, on the community-creation part: how granular should communities be?.