Hi Ledetele,
I think this is because you’re editing your articles with Social Articles plugin. Am I right? For more about this plugin, please visit the plugin’s website: social-articles.com.
In case you have some questions about the use of this plugin, don’t hesitate to reach the plugin’s authors by posting a topic on their support: Social Article Support.
If you want to use the default behaviour of WordPress, you have to create your articles in the WP Panel.
Hope this will help you. 🙂
Best,