superann

This plugin filters the sitewide comments feed as well as individual post comment feeds.
Upon first-time installation and activation, all trackbacks will be removed from the default WordPress comments feeds. 
You can override this behavior on the options page and also use the comments or trackbacks only feeds described below.
URL for comments only feeds: add the variable “comments” to your feed query string.
<ul>
<li>http://mysite.com/comments/feed/?comments</li>
<li>http://mysite.com/?feed=rss2&withcomments=1&comments</li>
</ul>
URL for trackbacks only feeds: add the variable “trackbacks” to your feed query string.
<ul>
<li>http://mysite.com/comments/feed/?trackbacks</li>
<li>http://mysite.com/?feed=rss2&withcomments=1&trackbacks</li>
</ul>

Separate Feed Comments and Trackbacks

Remove trackbacks from your sitewide and individual post comment feeds, and/or have alternate feeds for comments or trackbacks only.

LinksAlpha

Get Support: support@linksalpha.com
Plugin shows Twitter users who recently tweeted links from your blog. In other words, quick and easy way to get your Twitter community rolling 🙂
Plugin shows Tweets linking your Blog posts. Tweets show up below the comment form on each blog post
Plugin shows Count of Tweets linking to your blog. Count can be configured to show next to “Comment Count” or “Blog Post Date” for each blog post.
Check out our other plugins that you will find extremely useful:
<ul>
<li>Social Discussions: show popularity of your blog posts on Social Networks including Twitter, Facebook, Google Buzz, Yahoo, and bit.ly. https://wordpress.org/extend/plugins/social-discussions/</li>
<li>Social Stats: track your blog activity on social networks – monthly/weekly/daily, and track your popular posts. https://wordpress.org/extend/plugins/social-stats/screenshots/</li>
<li>Network Publisher: auto publish your blog posts to Twitter, Facebook, LinkedIn, Yahoo, Yammer, Identi.ca, and MySpace. https://wordpress.org/extend/plugins/network-publisher/</li>
<li>Buzz Roll: let your users share your blog post on fastest growing social hub – Google Buzz. https://wordpress.org/extend/plugins/buzz-roll/screenshots/</li>
</ul>

Separate Feed Comments and Trackbacks vs Retweeters