But that's the whole point: the is no centralised organisation. Which is the reason most of us are here. Duplication is just an unavoidable side-effect.

And it's not as if reddit were immune from that. Lots of similarly named subreddits on the same topic.

So that's not something that is "to be done". (Unless you meant TBH: to be honest.)

It's sort of the early days. I think this is an issue that will work itself out over time as people gravitate to the largest, most active communities for a topic and the smaller ones fade away. But with so many people arriving, trying to figure things out, and setting up their own communities for topics they like things are certainly kind of diffuse at the moment.