comment-padding

comment-padding is a variable defined in `newcomment.el'.
Its value is

" "

Documentation:
Padding string that `comment-region' puts between comment chars and text.
Can also be an integer which will be automatically turned into a string
of the corresponding number of spaces.

Extra spacing between the comment characters and the comment text
makes the comment easier to read. Default is 1. nil means 0.

You can customize this variable.