For the record I don’t think what OP describes would be right. But I am certain there are better ways to mesh together disparate feeds into one and have all discussion at least be cross-referenced - something better than just crossposting. Because while
1 million users discussing a topic spread out across 1000 communities of 1000 active users leads to more vibrant and meaningful discussions on that topic
May be true, it doesn’t hold true at smaller scales; a hundred users spread out across ten communities of ten active users each is pretty much a ghost town.