I wouldn't say anything and mind my own business most likely. But maybe I'd be a little creep and try to see what their username is :P
People use all kinds of social media/sites (reddit, twitter, etc) and I don't think ERA is too different or special. But I do wish more people were into message boards/forums, because they're really fun. I personally wouldn't mind if one of y'all approached me in public. I think it would be cool.
If we're standing or sitting like right next to each other for a long period of time I might say "how's it going?" and slowly introduce myself, and if they're nice I'll bring up the ERA thing. That would be a really rare "waiting room" interaction, though.