The first person to use @ as a description of directing a post at another user was Robert S. Andersen ("rsa") on 2 November 2006;[1][self-published source] initially, this usage made use of a space between the @ and the name, followed by a colon and the main content.
[citation needed] The first to propose a general syntax for directly addressing users in posts were Ben Darlow[2] and Neil Crosby,[3][original research?]
and by January 2007, more Twitter users began to take notice of the practice with various degrees of acceptance;[4][self-published source] within the year, the convention trended toward combining the @ and a Twitter username (as opposed to a real name) and prepending the combination to the beginning of a post in order to indicate a reply.
Twitter added support for "@replies" beginning in May 2008,[5][non-primary source needed] with any combination of @ with a username being turned into a hyperlink to the profile.
[6][non-primary source needed] Beginning September 2009, Facebook integrated the at sign as a mentioning feature; typing "@" in a post automatically initiates a drop-down autocomplete list containing names of "friends", groups and pages, which, after one being selected and the post published, links to the profile, group or page.