1º I answered the question, so I cannot claim disinterestedness. If pressed, I would probably claim fairness, but wouldn't we all?
2º A certain amount of the SE idealism runs into trouble in practice. For instance, it is hard to write a good question, and sometimes it's hard to read one well. I certainly read SE quickly and sometimes make mistakes. A good answer can bring out what is good about a question that might otherwise be hard to perceive. This has been discussed before.*
3º Another practical difficulty is reopening a closed question. That the system is biased against it, in practice, has been discussed before.*
4º Mods have reopened improved questions before, but they tend not to do it unilaterally, AFAIR. One particular case has been discussed before: when a (high-rep) user requests it because they feel they have an answer that would be useful for others (I forget the definition of high-rep, maybe 100 or 200 rep, maybe more, but not someone who just joined). Sometimes their actions irritate me...when I'm right and they're wrong. :)
5º I think it's difficult to separate out the qualities of the question itself and their relationship to the actions taken. It's an important point: To include such considerations will tend to favor one argument; to exclude them, another.
6º Re "Why" in the original title/final question: Why can you write "2x" instead of "2 x"?
In general, the question "Why is/does...?" is ambiguous. Usually the OP has something more specific in mind. Often OP's don't even care that much about "why?" but are really looking for correct code or workarounds. This time the OP was interested in a certain why question. I have to say my first reaction to the title was to skip it. After it got bumped a couple of times, I thought surely it'll be closed, and I read it to see what all the activity was about. It was a why question that theoretically could be answered, but since, as I remarked, "The documentation is notoriously incomplete," I wasn't sure a definitive answer would be found.
7º Not an opinion-based why question.
It was not a why question of the sort referred to by @rhermans in his comment (by my reading). The original question states "I'm looking for an official source to determine that [i.e. that
2x is valid syntax for denoting multiplication]." This is the justification (the why) that the OP was seeking. It is perfectly clear and not opinion-based. However, as I said, writing a good question is not easy, and this statement is buried in the middle, bracketed by the title and final "Why...?" I missed it at first, too, but saw @xzczd's rephrasing of the question in a comment (I answered before the question was edited). That the question was clearly not opinion-based, which was made even clearer by @xzczd's edit, makes me quite tolerant of the mod's action, an action that has let others add their good answers along side the answer I posted.
8º Not easily found in the documentation. Currently some of the close votes cite the "simple mistake" category. I think the answers prove it is not easily found in the documentation.
9º This question shows research effort; it is useful and clear... [the "hover text" for the upvote button on a question]. I think this is true, although I didn't at first. The "useful" attribute is arguable; but I think the question is sincere and valid, and I'm willing to accept them in place of useful. I came to this conclusion after a long debate with the OP about what exactly is in the documentation. It turns out the OP does not use the front end and perhaps doesn't have access to it. The OP was surprised that I did. The OP uses the online documentation only, and there are some slight differences between the HTML pages and the notebooks that are significant: in particular, spaces, the issue in the Q&A. The OP clearly had done some research in the online documentation, more perhaps than is behind most questions on the site (sadly). I surmise the OP is a relatively new user, and I think they should be excused for expecting that the documentation might contain a definition of the syntax of the language.
10º I think the "controversy" engendered by this meta Q&A, if that's not too exaggerated a characterization, has amplified the attention the question about
2x has received. It has gotten more votes, both upvotes and downvotes than it deserves. Normally such a question would have been overlooked by almost everyone. It's another example how ideal behavior is overshadowed by real behavior.
11º It's hard for me to get too excited about this issue because the question should have been reopened. Really, it shouldn't have been closed. The right decision was reached. The rest is moot. Wait for a time when it matters. Mistakes can be undone on this site (at least I think so).
*I haven't found references for the discussions I remember. (It's possible some discussion was in chat, too.) Here are a couple of related Q&A: