Perhaps keeping topics de-centralized is a key part of keeping systems from turning tyrannical. That’s the theory behind the term “totalitarian”: that too much unification of thought produces behavioral restrictions, via the justification that if the truth of each topic is known and indisputable, then there’s no reason to share power in society as long as the person in power knows the One Truth.
Centralized systems designed to uncover one clear answer, such as stack overflow, have every reason to fight against redundancy in answers. Anything rightly called a community though should not be built around the (totalitarian) idea that conversations are best centralized and made non-redundant.
Big important questions need to be rehashed millions of times, not just covered once with millions of audience members.