This plugin for sent information about comment to post author. 
Information about author name and author e-mails sets in custom fields for each post. 
In configuration of plugin you can set keys name for custom fields. By default this is “Author name” and “Author email”. 
Also can set subject and body of notification e-mail. 
In body of e-mail you can use macros:
[name] – name of authr from custom field 
[url] – post url 
[title] – post title 
[comment] – comment text

Comment Inform

This plugin for sent information about comment to post author. Infromation about authors gets from custom fields. Custom fields keys are "Author  …

belminf

Unique Comment Notify appends the comment author’s name to the subject of the 
notification message sent to the blogger. This prevents Gmail and other 
threading e-mail clients from grouping all notification e-mails for a post 
into one conversation.
<h3>Further documentation</h3>
Visit this <a href="http://wiki.bfworks.com/Unique_Comment_Notify" rel="nofollow ugc">project’s wiki page</a> for more documentation.
<h3>Release Notes</h3>
1.0: Initial publication of the plugin.

Unique Comment Notify

Unique Comment Notify appends the author's name to subject of notification e-mails.

Comment Inform vs Unique Comment Notify