I had an "@" after my name when I checked in at W Times Square. Didn't do much good (quite the contrary - I was questioned about this "Platinum chat room"...)
http://www.flyertalk.com/forum/Forum74/HTML/003707.html
Maybe our all-friendly Lurker adds the @ to our name/SPG-profile/something (I'm just guessing here) if we interact with him to help us, but some hotels misinterpret it as "customer prone to post complaints online"?