Addendum: At least on SO, when the code starts or ends with `, you need to add spaces inside of backticks on both sides.
That is, if you want foo`, you must spell it as `` foo` ``, not as ``foo` ``, because the latter incorrectly renders as foo` .
At most one whitespace is removed in this manner (from each side), so ` foo ` renders as foo .
Note that different rules apply inside comments. There, escape the backtick you want displayed, e.g. type `foo\`` to get foo` inside a comment. See the section Backticks within backticks at the end of this community wiki.