Will Brubaker

You’ve poured your heart and soul in to writing fascinating blog posts.  You know you have a lot of readership, but nobody except your mom is leaving comments.  That’s a bit discouraging right?  Entice your readers to leave comments by giving them a picture of a cute kitten in return.
Just prior to the comment form coming in to view, an unobtrusive panel will be displayed with a short message that says: “Your comments make us happy.  Leave a comment, get a kitten!”
 
When a comment is submitted, a picture of an adorable kitten is displayed in a modal window.
Caveats:
This plugin assumes that your comment form is A) built with the ‘comment_form’ WordPress function and B) that your comment form has an id of “commentform” (This is the WordPress default, but your theme developer may have changed the behavior for whatever reason. 
This plugin assumes that comment forms only appear on single posts and only loads the code when a single post (or page) is loaded. 
 
<h3>Other Information</h3>
I created this plugin for my own amusement and am offering it for you to use as you wish.  If you find it useful but would like more features, please do ask.

Kittens for Comments

Works well, customizable and just damn cute! Love it. =D



Awesome

Encourages your readers to leave comments with the promise of a kitten picture.  Who doesn't love kittens?

jp2112

Show Comment Policy lets you display a custom message above your site’s comment form. Display your blog comment policy or any other text you want your readers to see.
Use it for:
<ul>
<li>Comment policy</li>
<li>Posting rules</li>
<li>List of allowed HTML tags in comments</li>
</ul>
<h3>If you need help with this plugin</h3>
If this plugin breaks your site or just flat out does not work, please go to <a href="https://wordpress.org/plugins/show-comment-policy/#compatibility" rel="ugc">Compatibility</a> and click “Broken” after verifying your WordPress version and the version of the plugin you are using.
Then, create a thread in the <a href="https://wordpress.org/support/plugin/show-comment-policy" rel="ugc">Support</a> forum with a description of the issue. Make sure you are using the latest version of WordPress and the plugin before reporting issues, to be sure that the issue is with the current version and not with an older version where the issue may have already been fixed.
Please do not use the <a href="https://wordpress.org/support/view/plugin-reviews/show-comment-policy" rel="ugc">Reviews</a> section to report issues or request new features.

Show Comment Policy

Display your site's comment policy above the comment form.

Kittens for Comments vs Show Comment Policy