Let's say someone asks how to perform a task but does not specify what techniques/vi features they want to use to achieve the task. Then someone writes a fantastic answer using a particular feature.
How would we feel about adding the tag for that feature to the question, even though the question itself is not about the feature?
The documentation implies that the tags only refer to the question:
A tag is a keyword or label that categorizes your question with other, similar questions.
However, I feel like also including tags appropriate to the answers might be useful.