You can use LaTeX code to write your math in the comments. You can use $\$$your latex code\$$ for inline, and$\$\$$your latex code\\$$ for display. To number the formulas you can use the \tag command, like$\\$\$$your latex code \tag{your number}\\$$. If you need more advanced options check this page in MathJax Documentation. If you are curious, I am using “Simple Mathjax” plugin in WordPress.