I recently left a comment here containing the equation $$\sigma(i_1\;i_2\;\cdots\;i_n)\sigma^{-1}=(\sigma(i_1)\;\sigma(i_2)\;\cdots\;\sigma(i_n))$$ but the last $\sigma$ is broken, displaying instead as ${\color{red}\s}\;igma$. There is no space or invisible character seperating the s from igma.

The un-rendered of the comment:


It seems that if I add spaces around the equals sign, the comment renders correctly. Perhaps there is some length restriction on the parser that handles comments?

  • $\begingroup$ Illustration: $$\sigma(i_1\;i_2\;\cdots\;i_n)\sigma^{-1}=(\sigma(i_1)\;\sigma(i_2)\;\cdots\;\sigma(i_n))$$ $\endgroup$ Apr 14, 2014 at 1:14
  • $\begingroup$ Adding spaces around equals sign: $$\sigma(i_1\;i_2\;\cdots\;i_n)\sigma^{-1} = (\sigma(i_1)\;\sigma(i_2)\;\cdots\;\sigma(i_n))$$ $\endgroup$ Apr 14, 2014 at 1:15
  • $\begingroup$ This is definitely a duplicate. $\endgroup$
    – Asaf Karagila Mod
    Apr 14, 2014 at 2:00
  • $\begingroup$ @AsafKaragila Found it. $\endgroup$ Apr 14, 2014 at 2:04

1 Answer 1


This is StackExchange™ WhiteSpace EnforcementOfficer™ at work. Looking at the HTML source of the page, you'll see \s‌​igma there:

@abe15 The key is to know that $$\sigma(i_1\;i_2\;\cdots\;i_n)\sigma^{-1}=(\sigma(i_1)\;\sigma(i_2)\;\cdots\;\s‌​igma(i_n))$$

Inserting a space in LaTeX markup eliminates the (perceived) need for inserting ‌​.

  • $\begingroup$ Thanks, this is definitely the culprit. I wonder if there is a way to force breaks and not break mathjax? $\endgroup$ Apr 14, 2014 at 1:44
  • 1
    $\begingroup$ @AlexBecker The most logical way is probably to configure MathJax on SE to perform pre-parsing string replacement such as ‌​ $\to$ empty string (and & $\to$ &, to fix another issue). If this is done via parameters in the MathJax configuration script, the effect would be neatly localized to SE. I don't think introducing support for such parameters would be too much work for MathJax team, considering that SE is one of five Partners, with annual support level of $20,000. $\endgroup$
    – user127096
    Apr 14, 2014 at 1:58

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