Comment form was unaffected by installation and activation of this plugin. When comment form is submitted, comes back with an error that the text entered didn't match the CAPTCHA image, but if there's no CAPTCHA image and no field to enter it's text, user is unable to add comment.
As in the earlier thread, closed, I added the code to my comments.php file. This printed, verbatim, the code I entered. Clearly, the solution proposed doesn't work because it's not added to the documentation or FAQ.
Waste of time. Finding something else.