MathJax Usage Guidelines

Question

It's cool that we can use MathJax to do nice stuff like:

$$\{0+ai,0-ai^\frac{2}3,0+\frac{i}a,0-\frac{i}a\}\forall a \in A \subseteq \Bbb{R}$$

(stolen from this Jonathan Allan answer)

or this:

$$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}$$

(stolen from this Mathematics Meta answer).

But we also have MathJax being used in cases like this question or this question or this question or this question, where's it's simply rendering digits differently. Or this answer where it does indeed help the formatting a bit, but is nothing that couldn't be achieved/communicated with regular characters.

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Why this might matter

So who cares? Just use it or don't, as long as the question is clear. Point taken, imaginary reader, but there might be a few downsides to using MathJax if it's not strictly necessary.

• Based on this answer, any question with MathJax in the title will be automatically excluded from the Hot Network Questions.

• It can, at times, make search results look weird:

• Based on this answer, MathJax is likely to eliminate a question/answer from being used on the Tour page. _{Yes that is a very tiny problem.}

• Also doesn't seem like it works in "tooltips" on question hovering:

• As Alconja pointed out in comments, doesn't work in comments on mobile.

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So...

• Does this matter at all?
• Should we discourage and/or edit out uses of MathJax when they're not really necessary?
• Are there are general guidelines for when it is or isn't worth it to use MathJax? E.g., $x^2$ seems obviously better than x^2, but is $4-3=1$ that much better than 4 - 3 = 1?