comment in .info file of Drupal

you can use the semicolon:

; This is a comment

The character used as comment delimiter is reported in Writing .info files (Drupal 6.x):

info files may contain comments. The comment character is the semi-colon and denotes a comment at the beginning of a line. CVS Ids used to be placed at the head of info files using a semicolon, but now that Drupal.org has moved to git they are no longer included.

The equivalent book page for Drupal 7 (Writing .info files (Drupal 7.x)) reports the following sentence:

info files may contain comments. A semi-colon [;] placed at the beginning of a line makes that line a comment, and that line will not be parsed.