It is because this forum will display mathematic equation if you put some TeX syntax between dollar sign.
For example:
$ \alpha+ \beta +\Gamma $
will display
\alpha+ \beta +\Gamma
(It is similar to what will be display in EJS when you type equations in TeX format.  Because EJS code was compiled with java , so you need to add two backslashes to translate into one backslashes during the java string processing.)

You can also use _ and ^ to get subscript and superscript effect (and many more TeX mathematic equation features.)

If you want to display dollar sign, please add a backslash in front of dollar sign.
\$