What is the correct way of treating rare tags, say with a single occurence? I just figured out that tags without any occurrence are most likely synonyms (which is not obvious from the tag-overview page), but that's a different topic.
For some of the tags, it is obvious, that we should search all questions and add the tag (e.g. big-rip or spitzer-space-telescope) to the question, since most probably, the tag did not exist yet when some questions have been asked.
But what about the other tags (like anomaly, time-domain-astronomy, and many more, see screenshot) with a single occurrence? Should we discuss every single one of them?