I've noticed that some Japanese Twitter users put words/short sentences separated by an "@" symbol in the "name" field. A common one I've noticed is "abc123@LINEスタンプ販売中," which seems to imply they're selling stamps on LINE. Some even have multiple "@" symbols in between stuff.
It seems to be fairly common in the Japanese Twitterverse, so I'm hoping someone can shed some light on the matter. Thanks!