If you are using an older SharePoint site with an embedded Yammer conversation, as of March 5, 2018, some functionality will no longer be available.
You can't use @mention to make sure a specific person gets notified about your post. Instead, click Add people to notify .
When you copy and paste a link in your post, a preview for the link won't be created. There is no workaround.
This happens when your SharePoint site is set to use Internet Explorer 10 Document mode. This setting is controlled by your SharePoint site owner.
What are the system requirements for Yammer?
Yammer follows the Office 365 system requirements. Office 365 does not support Internet Explorer 10 or earlier versions.
What is Internet Explorer 10 document mode?
Document modes are used by web developers to specify which Internet Explorer versions a website is designed for. SharePoint site owners can choose compatibility with specific document modes.