You can do this with an advanced icon rule, something like this:
The template text is
Code:
program:
if $#long_comments_to_copy == $#gr_reviews then 'cry-icon.png' else '' fi
It does an exact case-insensitive match.
Personally, I would do this with a saved template search instead of an icon. With that I get the answer without scanning the booklist for the icon and there wouldn't be any performance hit. The search would be something like this:
