I always enjoy hearing others' thoughts on taxonomies, and Lea's ideas are well thought through and come with some interesting challenges (and findings) around using hackable URLs, folksonomies, and static site generators like Eleventy. All useful stuff!
On the issues of orphan tags (only used in one place):
It is important to note that orphan tags are not (always) an authoring mistake. While some tags are definitely too specific and thus unlikely to be used again, the vast majority of orphan tags are tags that could plausibly be used again, but it simply hasn’t happened.
And some UI ideas that Lea has been kicking around on how to handle them (including clustering them all in a disclosure pattern on their Tags page):
For now, I’ve refrained from making them links, and I’m displaying them faded out to communicate this.
Another alternative I’m contemplating is to hide them entirely. Not as a punitive measure because they have failed at their one purpose in life 😅, but because this would allow me to use tags liberally, and only what sticks would be displayed to the end user.
On the problem of considering tags to be a folksonomy, and therefore lacking hierarchy (i.e. a flat structure of labels):
I have yet to see a use case for tagging that does not result in implicit hierarchies.
And their conclusion around categories, which runs counter to my own, but makes a lot sense, given their context:
Lots to think about, but one thing seems clear: Categories do not have a clear purpose, and thus I’m doing away with them. For now, I have converted all past categories to tags, so that the additional metadata is not lost, and I will revisit how to best expose this metadata in the future.