"Code" formatted text in Markdown is indicated inline by putting the text between backquotes, or by indenting the text at least four spaces.
In the two examples below, I have typed a single backslash followed by a dollar sign, but Stack Exchange's edit preview rendered two backslashes followed by a dollar sign:
Here is inline single backslash followed by dollar sign:
Here is display **single** backslash followed by dollar sign: `\\\$`
After I save the article, SE renders the text with three backslashes before each dollar sign.
I think a single backslash followed by a dollar sign should render as a single backslash followed by a dollar sign, not as two or three backslashes followed by a dollar sign.
As written with single backslashes
As rendered (in preview) with two backslashes
As rendered (finally) with three backslashes
I am using Firefox 83.0 (64-bit) for Ubuntu.
This earlier question may be reporting the same thing but the description is unclear.