This feature will help users get unique usernames by the system in case the names did not exist or users could change this auto-generated usernames as to what they desire. The feature will not require any additional settings from community administrators or moderators. Settings related to privacy and security will not change either.
How it works: @mentions will function in line with commonly accepted Internet standards. A user typing @“user name” will see an auto-complete list of matching usernames to select from. The selected user will receive an email pointing towards the referenced content. In private campaigns it is not possible to send @mention notifications to members who do not have access to the campaign. This feature also has curse filtering applicable in case an inappropriate name is used as a user name.
On a successfully login to a community by a new user, a screen to set your profile/username pops up as shown in the image below

A user can use @mentions while commenting on an idea which looks like the image below.

It also can be used to mention while submitting an idea in the description field. 

@mention feature is also available to members who has access to Stage specific comments tab as well. For example: Build Stage, Review Stage Assessment Stage

A notification email is send to the particular user on being mentioned in the community.

Note:  SSO communities can pass usernames via ADFS as a SAML attribute and map it to username.

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