Off-topic, but this story by Wired shows how a fanfiction archive site, Archive of Our Own, does tagging and keeps tags relevant. In short, people can create tags but behind the scenes, curators work to see which tags are in current use and how to relate them to tags already created.
Obviously it’s a lot of work and probably overkill for this forum for now, but it’s an interesting example of an apparently effective tagging system. From the article:
AO3’s [Archive Of Our Own] trick is that it involves humans by design—around 350 volunteer tag wranglers in 2019, up from 160 people in 2012—who each spend a few hours a week deciding whether new tags should be treated as synonyms or subsets of existing tags, or simply left alone. AO3’s Tag Wrangling Chairs estimate that the group is on track to wrangle over 2 million never-before-used tags in 2019, up from around 1.5 million in 2018.
Laissez-faire and rigid tagging systems both fail because they assume too much—that users can create order from a completely open system, or that a predefined taxonomy can encompass every kind of tag a person might ever want. When these assumptions don’t pan out, it always seems to be the user’s fault. AO3’s beliefs about human nature are more pragmatic, like an architect designing pathways where pedestrians have begun wearing down the grass, recognizing how variation and standardization can fit together. The wrangler system is one where ordinary user behavior can be successful, a system which accepts that users periodically need help from someone with a bird’s-eye view of the larger picture.