GitHub-flavored Markdown does not use C-style escapes for escaping backticks inside spans. Instead, GFM uses double, significant whitespaced, backticks.
Two backticks, then a space, then a backtick, then a space, then two more backticks:
`` ` ``
produces:
`
Can you quote backticks inside a code block inside a GitHub issue title? Using double backticks as the delimiter doesn't work in that context.