NodeBB looks great for what it does: single-community forums. I'm wondering, however, whether it could be modified to support multiple communities without necessarily having separate instances of the software.
I was thinking you could treat categories as communities, but it doesn't look like NodeBB has a way for a user to "subscribe" to them such that their "front page" would simply be a list of populate posts for all of their subscribed categories.
Another worry would be scalability. It would seem like using a relational database would be better for tracking/parsing a lof of the data that a website of 100's of communities would need. (I'm NOT a DB expert by any means...just a hunch on my part).
Just wondering whether something like this should even be attempted or would simply creating this multi-community forum from scratch be a better approach.