I'm aware that I can use
(* ... *) to comment out stuff in a notebook. Many languages have a syntax for single-line comments, such as
//in C, C++, Java, C#, ...
#in shell, Python, ...
For example, in C++ you can write
int x = 5; // std::cout << "debug: x = " << x << std::endl; return x;
in which the second line is commented out.
Is there a way to quickly comment out just one line in Mathematica, without having to type paired comment characters?