The initial AuthImage install didn’t go according to plan. When the plug-in was installed, no image appeared – therefore no comments could be left, genuine or otherwise.

After scratching my head for some time, I remembered that this blog is in a separate folder from my WordPress installation. I checked back over the AuthImage code and sure enough, there was a line in my comments.php file:
“img src=”/wp-content/plugins/authimage.php”

When I changed it to:
“img src=”/wordpress/wp-content/plugins/authimage.php”

The image appeared, the code worked perfectly and comments can no longer be submitted without entering the randomly generated code.