Wikipedia has its hierarchical categories, for an example that is already working. More historically, the librarians have the Dewey decimal system and the subject classification system.
But it’s a good idea and may give the fediverse an edge until reddit copies it.
Gitea, GitHub and the like allow the owners of a repository to create an associated wiki by selecting a preference check box. You should be able to copy the relevant code from any free/open source implementation. It would be useful for providing Frequently Asked Questions for the community for example.
Can we have a text summary please?