There is an automatic job that deletes single-use tags after 6 months. No attempt is made at determining whether the tags are good and should remain, or whether the tags are a variant name of another tag and should be renamed or made synonyms. No attempt is made to retain tags that have proved their worth, for example with a tag wiki. There is no way to explicitly declare a tag as good. Even beta sites, where it is expected that the tag system is still evolving, are not exempt. This job is not subject to any review, not even after the fact: one day the tags are there, the next day they're gone.
The complete lack of logs from the tag killer makes it difficult to know whether the vanished tags were serving any function. Fortunately, for Super User, Jeff Atwood posted a list of tags killed by the initial run of the script.
I've taken a cursory look at this list, and I notice, in comparable proportions:
- Some truly bad tags (e.g. expectations, home-user, practical-joke), that are best killed. However, many of these are signs of a bad question or a question in need of other editing, so it would be better to manually review the affected question than silently retag them.
- Some tags that should have been renamed (explorer, raid-card, screnshot). No script can guess the right target tag, that would require manual review.
- Tags that were meaningful and but perhaps overspecific (aacs, medical-records, jnlp). These tags aren't a huge loss, but they are also not harmful. Furthermore, straight deleting them is wrong: the tag should be replaced by a more general tag.
- Tags that were definitely useful because they are about a specific program or other technology (bbc-micro, wifidog, nethack) which someone asking a question about the topic would naturally pick.
All in all, the data does not strongly justify removing single-use tags, and shows that their automatic removal causes significant harm. Please turn off the tag killer on SU.