@IsabelBeckenbach discovered why `\( \)`

isn't accepted as a math-mode delimiter on MO. I'd always thought it was a design choice, but apparently it's just a mis-escaped regex. I suggested that they promote their discovery to a bug report, and am only doing it myself because they do not seem to prefer to do so; but all credit for the discovery is theirs, and the following is quoted *literatim*:

I think the problem has something to do with the MathJax Configuration at mathoverflow:

```
<script type="text/x-mathjax-config">
MathJax.Hub.Config({"HTML-CSS": { preferredFont: "TeX", availableFonts: ["STIX","TeX"], linebreaks: { automatic:true }, EqnChunk: (MathJax.Hub.Browser.isMobile ? 10 : 50) },
tex2jax: { inlineMath: [ ["$", "$"], ["\\\\(","\\\\)"] ], displayMath: [ ["$$","$$"], ["\\[", "\\]"] ], processEscapes: true, ignoreClass: "tex2jax_ignore|dno" },
TeX: {
extensions: ["begingroup.js"],
noUndefined: { attributes: { mathcolor: "red", mathbackground: "#FFEEEE", mathsize: "90%" } },
Macros: { href: "{}" }
},
messageStyle: "none",
styles: { ".MathJax_Display, .MathJax_Preview, .MathJax_Preview > *": { "background": "inherit" } },
SEEditor: "mathjaxEditing"
});
```

In particular the deliminators for inline math are defined to be

```
[ ["$", "$"], ["\\\\(","\\\\)"]
```

E.g. when using

```
\\\\(L^ 1 \cap L^ \infty [0, \infty )\\\\)
```

one gets the correct mathjax rendering

\\(L^ 1 \cap L^ \infty [0, \infty )\\)

So, one should replace

```
[ ["$", "$"], ["\\\\(","\\\\)"] ]
```

by

```
[ ["$", "$"], ["\\(","\\)"] ]
```