You can mention other Hub users in any content you create by using the @ symbol. This is called an @mention. When you use @mention, the user you are mentioning will get a notification in their Communications stream. You can also @mention spaces or groups.
To use @mention:
1. In a piece of content, a status update, or comment, type the “@” symbol (or click the “@” icon if it is available) and start typing a person’s name. A search dialog opens and suggests possible matches.
2. Use an underscore “_” as a space to search for names or titles with multiple words. For example @David_B would match the Davids whose last names begin with “B.” Your picker will include documents, discussions, and places, as well as people. Keep typing to narrow the choices further.
3. Select the correct match from the list. The new link shows up in your content.