Normal text is being rendered as MathJax in comments

[kmk3]

In issue and discussion comments, normal text between dollar signs is being
rendered by MathJax. Example:

${HOME}/foo should be moved to ${HOME}/bar.

That is rendered as:

${HOME}/foo should be moved to ${HOME}/bar.

Where the text in the code span becomes visually mangled, it cannot be selected
and right-clicking it opens a weird macOS-looking JavaScript-based context menu
that contains an "About MathJax" item.

Even though the text is not inside a code block or anything of the sort.

Environment: Firefox 100 on Linux.

Relates to #2816.

[kmk3]

Note that as of writing, this behavior is not documented anywhere on the
CommonMark spec, nor on the GitHub Flavored Markdown (GFM) spec:

• https://spec.commonmark.org/0.30/ - Version 0.30 (2021-06-19)
• https://github.github.com/gfm/ - Version 0.29-gfm (2019-04-06)

[rusty-snake]

https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/writing-mathematical-expressions

[kmk3]

To use another programming-related resource for comparison, while multiple
sites on the Stack Exchange network enable the rendering of mathematical
expressions, it is not enabled on the more programming-focused sites, such as
on StackOverflow. Additionally, some of those sites that enable the math
rendering use different delimiters. From "Which Stack Exchange sites use
MathJax?":

These sites (and their respective Meta sites) support MathJax:

• [...]
• Biology (with mhchem extension)
• Blender
• Chemistry (with mhchem extension)
• Code Golf (with \$ delimiters)
• Code Review (with \$ delimiters)
• [...]
• Earth Science (with mhchem extension)
• Economics
• Electrical Engineering (with \$ delimiters)
• Engineering
• Game Development (with \$ delimiters)
• [...]
• Matter Modeling (with mhchem extension)
• [...]
• Role-playing Games (with \$ delimiters)

[PythonCoderAS]

Honestly I think there should at least be a per-repo/maybe even per-file way to turn this feature on or off.

[zakaryarashak]

17522

[rusty-snake]

https://github.blog/changelog/2022-05-19-render-mathematical-expressions-in-markdown/

It's a feature 😉

[andrensairr]

I discovered GitHub's new feature quite by accident having made the simple but fatal mistake of using two $ signs in an issue comment. I'm all for new features, and I understand there are many who have long desired it, but I'm sure this won't be helpful for everybody and without a better way to explicitly markup math expressions, the approach taken runs the risk of breaking a heap of historical comments, not to mention confusing users of simple cases like myself.

As a work-around the dollar signs can be escaped by wrapping in <span> tags, a feature designed to avoid confusing the renderer when writing a $ signs inline with math expressions, but I think this is a heavy price to pay to opt out of the feature. Using the backslash (a la \$) might have been a good choice, but alas this only works within a math expression.

[joshjohanning]

I agree, if you have a two dollar signs in a line, it (sometimes) renders everything in between as math.

Seems to be for example if you put a period right after a dollar sign and already have a dollar sign in the sentence. See:

This renders incorrect:

Hi, I would like to buy your apples but they are $1, I only have $.75, can I buy 1?

Hi, I would like to buy your apples but they are $1, I only have $.75, can I buy 1?

This renders correctly:

Hi, I would like to buy your apples but they are $1, I only have $0.75, can I buy 1?

Hi, I would like to buy your apples but they are $1, I only have $0.75, can I buy 1?

[bence-toth]

According to the documentation it is now recommended to use <span>$</span> to opt out of MathJax formatting on lines with multiple dollar signs:

E.g.:

<span>$</span>{HOME}/foo should be moved to ${HOME}/bar.

Will be rendered as:

${HOME}/foo should be moved to ${HOME}/bar.

[rusty-snake]

Shorter alternative:

${HOME}/foo

${HOME}/foo

[rusty-snake]

New alternative syntax (which doesn't seem to work):

https://github.blog/changelog/2022-06-28-fenced-block-syntax-for-mathematical-expressions

```math
\sqrt{5}
```

$$\sqrt{5}$$