What special delimiter is NOT used for comment lines?

The correct answer is the dollar sign ($) because, in most programming languages and scripting contexts, it is not used as a delimiter for comments.

In many programming languages, the hash (#) is commonly used to denote comments. For example, in languages like Python and shell scripting, anything following a # on the same line is ignored by the interpreter. Similarly, the double slash (//) is standard in languages like C++, Java, and JavaScript, where it indicates that the remainder of the line is a comment. The semicolon (;) is often used in languages such as C and C++ to end statements but can also serve as a comment delimiter when used in certain contexts or languages.

The dollar sign, however, does not serve as a comment delimiter in these contexts and does not indicate any comment functionality in the majority of programming languages, making it the correct choice for the question asked.