I was wondering if a policy exists (and if so, what it is) for retagging questions once they have been answered. To illustrate what I mean, I recently answered Draw small cross at the center of the page. It is currently tagged as technical-drawing, perhaps the positioning tag would have been better, but that is not the point I want to make here. The answer I provided (which was accepted) was a pure TikZ answer. Should the tikz-pgf tag be added to the question based on the accepted answer?
I suppose in part this question is about why are questions tagged a certain way? To make it easier for people with significant knowledge in a certain area to find the questions in order to answer them? Or also for people with a general interest in an area to find the questions? If the former is the case, tagging after a question has been answered has little use, in case of the latter it could still be valuable.