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?

xhtmlweaver

This plugin can greatly improve the user experience for your blog, by automatically and periodically saving the “just typed comment” for your visitors (the content textarea input box in comment section). The just typed comment is saved into browser’s local storage system to prevent loss of any unsubmitted comment from your visitors and doesn’t require any backend support.
This is similar like WordPress can remember your Name, Email, Website in comment area for the next visit, but WP Local Storage plugin extends this into next level, it can remember the actual unsaved comment (i.e. before hit submit button) so even the browser is crashed before the user hit save, it is okay! When the user came back, all “just type comment” will be still in there.
Full Support is available at http://www.xhtmlweaver.com or wp-support@xhtmlweaver.com

WP Local Storage

This plugin automatically and periodically saves the "just typed comment" for visitors so no data will be lost even the browser crashed.

Kittens for Comments vs WP Local Storage