The only reason this was posted was because of one massively upvoted post. There are 105 subscribers, and there was one post with 234 upvotes, so the ratio of MAU to subscribers went up really high.

I don't think duplication of communities is automatically a bad thing. You can always subscribe to multiple ones. It's bad for there to be ghost communities cluttering up the list, but I don't thing it's realistic to be able to stop that from happening unfortunately. I think the big thing is making it possible to find the still-alive communities. Of course too many ghost communities makes that a little inconvenient.

Other general thoughts: There's going to be an optimum size for a community, where it's big enough to spur activity, but not so large that the moderation becomes burdensome and the social contract among the participants starts to erode. There's no difficulty in subscribing to multiple communities on multiple servers. To me, looking over the community, list, it looks like the sweet spot is from 1,000 to 5,000 MAU. Any less, and the community starts to feel empty, and any more and it starts to get crowded and chaotic.

It might be good to take something like that into account when posting these lists. Right now it's just that one metric, which seems fine, but it might be good to try to be more sophisticated with it.

It might be good to try to make a tool which detects what communities someone might be interested in, that they don't seem to be aware of, and either post or send it to them as a DM. There's a lot you can do with data mining to figure out and prompt people for what they might be interested in.

It might be good to have a way to list out all the similar communities to any particular community, and what its status is, and in particular if it seems abandoned, as a way of recommending that it get shut down or not widely used. Maybe a persistent big list of nice communities with some hybrid of automation and human curation.