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This plugin allows you to add authentication using social media networks (Twitter, WordPress, Google+, etc.) for the users who want to comment on your blog. 
The plugin can be activated to provide authentication for all posts or only for selected posts. 
The usage of this plugin does not oblige you to create an account on our website, like others plugins do. 
All you need is to have an account (if you don’t have one, then you must create it) on the social network that you want to use as a source of authentication.
<h3>Configuration</h3>
To configure the plugin, you must follow the instructions described here: http://www.ixtendo.com/comments-with-social-login-wp-plugin/

Comments with Social Login

Add authentication using social media networks (Twitter, WordPress, Google+, etc.) for blog comments

soychuy

YouTube Thumbnail to Featured Image, as its name says, is a plugin that helps you to set a YouTube video thumbnail as a featured image of a post. The user just have to set a YouTube video URL and the plugin will do the rest.
The video thumbnail will be imported to your media library, so you can use it anywhere else.

Youtube Thumbnail as Featured Image

Use a YouTube Thumbnail as a Featured Image for a WordPress Post. You only have to set a YouTue Video URL and the plugin does the rest.

Comments with Social Login vs Youtube Thumbnail as Featured Image