A message source file should contain comments to help the translator in the process of translation. These comments will not be part of the message catalog generated. The comments are similar to C language comments to help document a program. A dollar sign ($) followed by a space will be interpreted by the translation tool and the gencat command as comments. The following is an example of a comment line in a message source file.
$ This is a comment
Use comment lines to tell translators and writers what variables, such as %s, %c, and %d, represent. For example, note whether the variable refers to such things as a user, file, directory, or flag.
Place the comment line directly beneath the message to which it refers, rather than at the bottom of the message catalog. Global comments for an entire set can be placed directly below the $set directive in the source file.
Specify in a comment line any messages within the message catalog that are obsolete.