You cite MathOverflow as an excellent community, and I agree. Joel Spolsky (Joel on Software, and later founder of StackOverflow) gave a talk on the The Cultural Anthropology of Stack Exchange and how they attracted and maintain communities. The talk starts off with a criticism of deeply nested replies. I disagreed with that criticism, but found the rest of the talk concrete and lucid.
You cite MathOverflow as an excellent community, and I agree. Joel Spolsky (Joel on Software, and later founder of StackOverflow) gave a talk on the The Cultural Anthropology of Stack Exchange and how they attracted and maintain communities. The talk starts off with a criticism of deeply nested replies. I disagreed with that criticism, but found the rest of the talk concrete and lucid.