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.

Lew Ayotte

Ever had someone comment on a post on your site that is really old? With the Advanced Comment Control plugin you can automatically disable commenting on old posts, or only allow certain roles to comment on certain post types. This is one of the easiest ways to handle spam and trolls.
What can you do with the Advanced Comment Control plugin for WordPress?
<ul>
<li>Disable comments on select post types older than a certain date.</li>
<li>Disable comments on select post types with more than a set number of comments.</li>
<li>Disable pings/trackbacks on select post types older than a certain date.</li>
<li>Disable pings/trackbacks on select post types with more than a set number of comments.</li>
<li>Set roles that can always comment on select post types.</li>
<li>Set roles that can never comment on select post types.</li>
<li>Set rules for logged in or logged out users.</li>
</ul>
You can follow the development of this plugin at <a href="https://github.com/lewayotte/advanced-comment-control" rel="nofollow ugc">GitHub</a>!

Advanced Comment Control

Easily control who can comment and when they can comment on any post type.

Separate Feed Comments and Trackbacks vs Advanced Comment Control