I installed qPloneComments (2.3.1) on Plone (2.5.3) and Zope (2.9.7).  After installing in the products directory, restarting Zope, and installing via the Quickinstaller (and configuring to enable anonyomous comments), an "add comment" box visibly appears for an anonymous end-user.  After clicking, the following appears (but I get an error at the top that says "Please correct the indicated errors"):

Add comment

You can add a comment by filling out the form below. Plain text formatting.

Note: you are not logged in. You may optionally enter your username and password below. If you don't enter your username and password below, this comment will be posted as the 'Anonymous User'.

Name

Password

Enter the word below (Required)

 

Please write versions of additional installed products (qPloneCaptchas) and all settings of qPloneComments (they appears in /prefs_comments_setup_form)

Go to "Site Setup" -> "Add/Remove Products", select "qPloneComments" and click "uninstall", then select "qPloneComments" and click "install" )