Konstantin Obenland

This plugin needs Jetpack by WordPress.com to be activated and its Sharing module to be enabled. 
Enter the desired Twitter usernamen in Settings -> Sharing. It will then be appended, every time a visitor shares your content on Twitter
See the <a href="https://dev.twitter.com/docs/tweet-button" title="Tweet Button" rel="nofollow ugc">Tweet Button documentation</a> for details.
<h4>Translations</h4>
I will be more than happy to update the plugin with new locales, as soon as I receive them! 
Currently available in:
<ul>
<li>English</li>
</ul>

Jetpack Twitter Via

Adds 'via @username' to the Tweet Button provided in "Jetpack by WordPress.com"

Brandon Kraft

Jetpack automatically disables its Open Graph tags when there’s a known plugin that already adds Open Graph tags, which is good. Sometimes, though, you might want to use Jetpack’s version instead. Even if you disable the tags in the conflicting plugin, Jetpack won’t add Open Graph tags without being told to do so.
This is great for when you want to use the awesome WP SEO by Yoast plugin or others like All-in-One SEO, but, for whatever reason, would like to use Jetpack’s OG tags instead.

Always Use Open Graph with Jetpack

Jetpack automatically disables its Open Graph tags when there's a known plugin that already adds Open Graph tags, which is good.

Jetpack Twitter Via vs Always Use Open Graph with Jetpack