Description
UPDATE
Now you can set an option in the new settings page (titled “Herc Sentiment” in the admin bar) to auto-approve positive comments, or un-approve negative comments.
Hercules Sentiment Analysis uses PHP Insight (https://github.com/JWHennessey/phpInsight) to determine whether comments, posts, and post titles are positive, negative, or neutral. This will help bloggers respond to readers who have concerns faster (or delete negative comments if necessary), as well as know what sentiment they are portraying with their post titles and content.
Screenshots
This is what the sentiment looks like on the comments table. 
This is what the sentiment columns look like on the posts table.
Installation
Add this plugin by uploading the zip using the “Add Plugin” feature built into WordPress. Otherwise manaully unzip the folder and upload the entire directory to your blog’s plugins folder ( /wp-content/plugins/ ). Next you have to activate the plugin.
FAQ
Where do I see the sentiment?
In the admin area if you go to the Comments or Posts page you will see columns where the sentiment will show up.
Reviews
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Contributors & Developers
“Hercules Sentiment Analysis” is open source software. The following people have contributed to this plugin.
Contributors
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Interested in development?
Browse the code, check out the SVN repository, or subscribe to the development log by RSS.
Changelog
1.2 – Added option to auto-approve positive comments, or auto unapprove negative comments.