Yes you can add @mentions to social posts created in Contentware. You can @mention organizations, but not individuals.
To add an @mention to a Twitter posts type the "@" symbol, then start typing the name of the organization. The "type ahead" function will show you a drop down of organizations which you can select from.
To add an @mention to a Linked post, type the "@" symbol then type in the FULL organization name. "Type ahead" functionality is not yet fully implemented in Contentware for LinkedIn.
@mentions are currently not available for Facebook. We are working to add this functionality as soon as possible.