WPMU DEV GLOBAL AUTHOR COMMENTS FEED Plugin
Provides a global feed of comments from a single author made across multiple sites on your network.
WPMU DEV GLOBAL AUTHOR COMMENTS FEED Plugin pulls every comment by a single user, across an entire network, into one feed.
This plugin is built to take advantage of Comment Indexer.
If you have a user posting comments to multiple sites on your network, and are looking for a way to catch them in a single feed, this is the plugin you are looking for.
Please visit official plugin page for more information