I don't think it's a problem or a feature. It's exactly what we saw on Reddit before it grew. It's not like Reddit had a limit on the number of subreddits a topic could have. As far as I'm concerned it'll eventually sort itself out just like it did on Reddit. It'll just take time to establish which communities are the largest. Eventually people will stop posting/subscribing to the communities that don't have as many people, and the largest one(s) will win out, just like they did on Reddit. This is an issue that requires patience. In the meantime, subscribe to them all and post to the one that has the most subscribers just like you would on Reddit if there wasn't a clear central community.