However, NodeBB and Discourse are both somewhere closer to the middle, but on the opposite sides. In both you will find categories and tags, but from what I've seen the emphasis is different - NodeBB is categories that can have tags, Discourse is tags that can have categories 🙂
Hah, this is funny, because that is entirely correct. Discourse wanted to take a hard left at what made forums... well, forums. They took a gamble on thinking that a tag-based approach was superior.
We found that a more traditional hierarchy made more sense from both an accessibility and from an archival standpoint.
It's also easier to support tagging as a separate first-class citizen, as opposed to trying to make tags hierarchical, which is what Discourse tried to do.
Were they successful? You decide 🙂