Link: Fans Are Better Than Tech at Organizing Information Online
The article explaining the tag wrageling process at the AO3. The AO3 allows people to tag whichever way they want, and the people then check, if some of the tags mean the same or are the subset of the already existing tags.
This avoids both the inflexibility of the predefined tags and the problem of tagging the same thing with the dozens of tags.
They were also a bit skeptical, that this could be replace by AI in the near future.