Programming enterprise apps and their supporting processes, I've used at several languages. Most of them have different ways to make comments.
|Characters||Languages||Multi-line vs. Single-line||Characters|
|/* */||C#, SQL, CSS||Multi||2,2|
|XML, HTML||Multi||4, 3|
|<%-- --%>||ASP.Net||Multi||4, 4|
|--||SQL (single line)||Single||2|
I didn't have any big dialogue on this, I just found it interesting - 7 different ways to comment code for a set of languages that are often used together for a common goal. I'm sure that someone with a strong Compiler background could explain the significance of multi-line comments vs. single-line comments, and number of characters involved to create the comment identifier.