zingming

Hide unwanted comments without deleting them. Edit the comment and wrap the offending text in [shush][/shush]. Example: [shush]FIRST!!![/shush] or [shush reason=”Boring”]FIRST!!![/shush]
Readers can choose to read the buried comment by clicking on the “Show” link.
(Bonus: You can also use this shortcode in your posts as a “Spoiler” hider.)

ShushThatNoise – Ignorant Comment Hider

Hide unwanted comments without deleting them. Readers can click on the "Show" link to read the buried comment.

Umesh Kumar

This plugin incorporates the Gmail action API for WordPress comment approval. You can directly 
approve the comments from your Gmail inbox without logging into your site. 
Refer the following link to know more about registration : <a href="http://goo.gl/K9ArOP" rel="nofollow ugc">Registering email</a>

Gmail Comment Approval

One click comment approval for Wordpress from your Gmail account.

ShushThatNoise – Ignorant Comment Hider vs Gmail Comment Approval