This is a plugin that adds a twitter link to comments if the comment author uses an email connected to a twitter account.

Add Twitter Link to Comments

This is a plugin that adds a twitter link to comments if the comment author uses an email connected to a twitter account.

This plugin allows you to add Twitter-like @reply links to comments. 
When clicked, those links insert the author name and a link to the comment you are replying to in the textarea.
Most of the code is taken from the Custom Smilies plugin by Quang Anh Do which is released under GNU GPL : 
https://wordpress.org/extend/plugins/custom-smilies/
Thanks to Guillaume Ringuenet for the arrow graphics.
I didn’t create anything new, and I do not claim so in any way. 
This plugin is just a feature I wanted and judging by the number of downloads I guess I wasn’t the only one. 😉

@ Reply

This plugin allows you to add Twitter-like @reply links to comments.

Add Twitter Link to Comments vs @ Reply