We switched up how we handle communities a couple times. We didnt start expanding horizontally until the main communities seemed stable and had some good activity (community creation was open publicly starting last month and before that there was the request zone). The posting activity is the same as it was in the previous systems, people just dont want to post and theres the 10% of people comment, 1% of people are posters rule (if its 5-6 posts per hour thats better than the past system as well)
The ones that are visible in new communities are empty mostly because they were just made (~ 100 coms made in the last month). The ones made by me and that are now handled by the vacant account are ones that have sources I can add to my rss reader and then post consistently. For example the elm community has weekly posts on things going on in the ecosystem. This means they wont be dead and should have a solid stream of posts as it builds up active users. Theyre made so they can start collecting people and subs over time rather than attempt to diverge and have nobody know to move over or people not joining at all since they looked for the language by name and didnt find anything (and then I assume people dont want misc changelogs of bug fixes posted to c/programming as well)
The most commonly used sorts in the instance are subscribed sort and local sort. If something is posted in one of the smaller communities people will interact with it in local sort. Crossposting is also highly recommended. I can maybe somehow make that more apparent than it already is
I think the better option rather than condense things into less communities is to crosspost things between the larger communities and the smaller communities and make the larger communities more apparent to funnel people into them
We tried the system with people interested in running it with the request system, it didnt work and people didnt actually boost things
Mac is my posting account. I can start crossposting a bunch of stuff I post on it into the general communities if the specific things have less than 100 active users and do some more discussion posts