I've thought a good bit about the "too large" side (author here under a different name). The magic rule for me has been to consider whether each member actually has a function within the community, in the sense that they contribute something unique to the group which is not contributed by anyone else, and for which the community would be hurt if they aren't there. The idea was originally put into my head by C.S. Lewis, in his work on Membership: "If you subtract any one member, you have not simply reduced the family in number; you have inflicted an injury on its structure. Its unity is a unity of unlikes, almost of incommensurables." E.g. if you were to remove a random poster from HN, it wouldn't affect anything much at all, because they end up a number. However, if you were to remove dang, their presence would be missed because they contribute to the uniqueness of HN's community in some way. IMO, if the group doesn't pass this test, you haven't actually found the real community yet.
Of course, all of this is quickly-written thoughts for a HN post. Maybe at some point I'll edit them down and post them properly, but I need to discuss it with more people so I'm sure my thoughts actually strike reality.
Of course, all of this is quickly-written thoughts for a HN post. Maybe at some point I'll edit them down and post them properly, but I need to discuss it with more people so I'm sure my thoughts actually strike reality.