I can see many instances where this is the case, but here's the most common scenario I encounter:
A user asks a question about query_posts() or get_posts() but the correct answer should use WP_Query or pre_get_posts.
Should the question get retagged with the proper technique? If so, I imagine it would be in addition to the original tag.
There was a question on Meta.SO a long time ago: Should we retag questions with topics proposed in the answers? where the accepted answer says No.
But … if someone is asking for an attempted solution without understanding the actual problem the answer may be very different from the original wording of the question (see What is the XY problem?). I think it is useful to find such answers via tags.
When I'm searching for examples of 'pre_get_posts' filters (I actually did that) then those answers should not be hidden due to a over-restrictive tag policy. That's why I tag content, not just questions. Make it easy to find good content.
Using query_posts() as the example: if the correct/accepted answer uses a different function - more accurately, uses a more correct implementation technique, then I say yes: re-tag the question. But more importantly, you should also edit the question to reflect a more-general question.
To generalize the example, I see this as a case where a user asks, "how do I use this not-best-case (or worse, wrong) implementation method to do X?", and the community responds with an explanation regarding why the OP's implementation method is wrong, along with a solution using the correct/best-practice method. In such cases, it is useful to generalize the question, and re-tag.
I don't know how far that answer extends to other use cases/scenarios, though.
query_posts() itself, which, based on core-developer comments, may one day soon die in a fire. A better example of a similar question might be one that asks, "how do I modify core to...?". We might be3 able to find examples of such questions that would fit this discussion.
Commented
May 14, 2012 at 15:30
No, not usually. The tags refer to the question, not the answers. People searching WPSE will be looking for similar questions (or browsing by tag) - either way, if their question is 'should I use query_posts() they won't be searching for pre_get_posts.
In fact, its exactly when the answers correct a bad practise, that these tags become very useful, pointing others to the 'correct' practise.
