That icon denotes a thread you have subscribed to, NamePros most likely has it so you automatically subscribe to a thread when you have posted a reply or started a thread. If you would like that to happen, click on User CP -> Edit Options -> Default Thread Subscription Mode, then change the drop down box to the form of automatic thread subscription you would like.
I will look into finding a vbulletin mod which can show which thread each user has posted in.
Clicking your User CP link shows you your unread subscribed threads if that helps.