MathJax on simple numbers, the HNQ and a game of 21

Question

In question titles, should "simple numbers" – those numbers that stand on their own and which do not require any $\TeX$ symbols to express cleanly – be put into MathJax anyway? Examples include 21 and 0.5.

On 1 March 2019 I answered a question in one of my pet topics: Is there any other number that has similar properties as $21$? The question got onto HNQ, and I edited the question's title twice in keeping with my intention to have no MathJax formatting around 21.

I was then suspended for a week, and I find the suspension silly.

After the end of said suspension I had a look at the meta questions and found this answer, which explains how questions with MathJax in their titles are excluded from HNQ and illustrates a possible consequence – something I had figured out by myself very early on. It says

I think this aspect [MathJax in title excludes a question from HNQ] should be considered when editing questions that can be useful to a broader audience, especially when the benefit of markup is purely cosmetic.

The reason given for my suspension was that I was promoting my answers by making irrelevant edits to the title to remove the MathJax. But I disagree with that reason. Before any edits, the 21 question's title did not have any MathJax. 21 versus $21$ is a purely cosmetic change, and I believed in good faith that the question would be useful more generally, so I hold that I was working to improve the formatting with my edits relevantly, and that adding MathJax here is superfluous.

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My convention is to not put MathJax around simple numbers. I remember that MathWorld follows a similar practice, and I have two reasons for adhering to it:

• The MathJax fonts are different from the fonts used to render normal text, so looks slightly unnatural if it's a simple number that is under the formatting. Compare "42 centimetres" against "$42$ centimetres".
• Most of my answers are typed on the Android app, so I can answer on the go and exercise my brain (my mid-term tests at the National University of Singapore in mathematics and computer science were coming up at the time of my suspension). The $ and \ characters require multiple touches, so in the interests of time I avoid them if doing so does not affect the quality of the formatting.

Answer 1

The job of $\rm\LaTeX$ is to separate the mathematics from the text. This makes it easier to immediately grasp and understand which part of the text is the mathematical part.

The text, however, includes the title.

The intersection of 2 sets is empty

If almost fine, because 2 is not there in a "mathematical capacity". (In general single digit numbers should be spelled out in these situation.)

In contrast,

How many 3 x 3 matrices are there over the field with 2 elements?

Should be in $\rm\LaTeX$, because $3\times 3$ stands out more, and in this case I would even consider putting the 2 in $\rm\LaTeX$ (or even replacing the whole phrase with $\Bbb F_2$ or $\Bbb{Z/2Z}$).

Doing these kind of thing is not a silly formatting meant to take your answer off the HNQ, it is meant to make the question more readable in a quicker way.

This is exactly the same reason why you won't use $\varepsilon$ to denote a natural number in analysis, or use $\pi$ to denote a finite set of algebraic numbers in number theory. You could argue that those are just letters and that is justified, and you'd be right. But we learn to take context-hints from the notation and text we read. Which is why mathematical parts of a question including the title should be written in $\rm\LaTeX$.