Julian Yanover

Check comments for duplicate content using Google AJAX Search API as they are published. This helps to avoid having duplicate content in your posts. It only checks approved comments that have over 50 words. The plugin searches two random strings, both 8 words length. If one of them finds an exact match, it emails you letting you know so you can check it yourself and decide if you want to delete it.

No Duplicate Content in Comments

Check comments for duplicate content using Google AJAX Search API as they are published. Emails you whenever it finds a match so you can check it and  …

Copyscape

The Copyscape Premium plugin lets you check if a WordPress post is original before it’s published, by using the Copyscape Premium API to check for duplicate content on the web.
The plugin will add a ‘Copyscape Check’ button to your WordPress interface, allowing you to check your posts whenever you wish. You may also set the plugin to automatically check your posts when you click ‘Publish’ and/or ‘Update’.
When duplicate content is found, a report of matching pages is shown. You may also see a detailed comparison that highlights your content on the found page.
If you do not already have a Copyscape Premium account, please <a href="http://www.copyscape.com/redirect/?to=prosignup" title="Copyscape Premium sign up" rel="nofollow ugc">sign up</a>, <a href="http://www.copyscape.com/redirect/?to=propurchase" title="Purchase Copyscape Premium Credits" rel="nofollow ugc">purchase some credits</a>, and enable your <a href="http://www.copyscape.com/redirect/?to=apiconfigure#key" title="Copyscape Premium API page" rel="nofollow ugc">API access</a>. You may then begin using the plugin.

Copyscape Premium

The Copyscape Premium plugin lets you check if a WordPress post is unique before it's published, by searching for duplicate content on the web.

No Duplicate Content in Comments vs Copyscape Premium