What Does This Mean?

Help!
  1. Look at the thing right after @roaringsoftly's and @jhope71's names. What is that symbol?
  2. Here it is even closer.
  3. It's not on everyone's name. Did you two put it there? Of not, what is it?
  4. Am I dumb for not knowing what that thing is or what it means?
    Geez, it doesn't mean I stalk them or anything, right? Because I don't.
  5. Help!