In fact I want to make some major tidy-up of some tags.
Because I discover that many MSE users are having some problem habitats that like to tag their questions without careful considerations, they like either tag their questions with ''wide scope tags'' only or tag their questions with both ''wide scope tags'' and ''narrow scope tags'' , causing the ''wide scope tags'' often have too many questions but the ''narrow scope tags'' often have too few questions, reduce the efficiency of tag-using.
Typical examples are the tags of linear-algebra series, the linear-algebra tag has nearly $10000$ questions, the matrices tag has nearly $5000$ questions, but for example the block-matrices tag and the random-matrices tag have only less than $100$ questions. The situation of the tags of linear-algebra series is alarming, as these will bring some large problems. For example the advanced-level questions such as about matrix functions and matrix equations will often fall into the oceans of ''wide scope tags'' such as the linear-algebra tag and often difficult to search them.
The tagging management system in MSE is so poor. The tagging rules in MSE is too generous. First, there are no punishment rules about inappropriate tagging behaviours. Second, as most MSE users often very busy on answering many questions to raising level to eventually become "top-level users" (reputations $>20000$ or even in multiples of $10^5$), or they are often afraid retagging will make OP unsatisfied or bump-up the questions and may make other users unsatisfied, therefore very less users take actions of both minor retagging or major retagging, with is often condisered as noxious by most MSE users.
So I decided to make some major retagging.
By recognizing some properties:
matrix-equations $\subseteq$ matrices $\approx\subseteq$ linear-algebra
matrix-functions $\subseteq$ matrices $\approx\subseteq$ linear-algebra
So my first operation is to create a matrix-equations tag, searching the questions about matrix equations and add the matrix-equations tag but removing the matrices tag and the linear-algebra tag on them to bypass the horrible usages of the matrices tag and the linear-algebra tag. For other matrix questions, keep the matrices tag but removing the linear-algebra tag on them to bypass the horrible usage of the linear-algebra tag.
The result is quite well. I found more than $100$ known questions about matrix equations.
However, my operation makes some MSE users unsatisfied. Jared made an application of the matrix-equations tag merge into the matrices tag (https://math.stackexchange.com/tags/synonyms). Landscape made rollbacks on most of the questions tagged matrix-equations (https://math.stackexchange.com/users/46120/landscape?tab=activity&sort=revisions). They both try to against my operation.
I don't understand why there are so many people like either tag their questions with ''wide scope tags'' only or tag their questions with both ''wide scope tags'' and ''narrow scope tags''. They should not be a good practice of categorization. Good categorization practice should be "categorize from specific to general" . Applying on our tagging system, the good tagging practice should be using the tags that are as specific as possible. ''wide scope tags'' should not use without careful considerations, unless you find that no ''narrow scope tags'' fits for your questions, otherwise many tags should require to use on each question.
Moreover, most mathematical branch names, e.g. algebra, linear algebra, calculus, etc. are no longer suitable to use as tag names, as they are too general to have too many questions belong to. They are better to upgrade as zone names.
So MSE is better to modify the system as "main page holds zones, zones hold tags" concept (i.e. the categorization system like http://answers.yahoo.com), to face growing numbers of questions. A few years ago the algebra tag has been blacklisted (The use of the [algebra] tag). I think we should consider doing a similar thing on e.g. linear-algebra tag and calculus tag.