nickgrossman

Enable commenting on your posts via Twitter.
Posts will get a “Discuss on Twitter” button, which will prompt visitors to reply to the original tweet about the post, as well as a “View Discussions” button which will link to existing tweets about the post.
Each new post will be auto-tweeted (requires the <a href="https://wordpress.org/plugins/wp-to-twitter/" rel="ugc">WP to Twitter</a> plugin and a <a href="https://developer.twitter.com/" rel="nofollow ugc">Twitter Developer account</a>).

Discuss on Twitter

neon

If you write something like “@nick, how are you?” this plugin will search for @nick’s url in the comment list of the current post and will convert his/her name to a link.

Twitter style links

This plugin allows you to add Twitter style links to comments.

Discuss on Twitter vs Twitter style links