I'll wave back, too! It was this event that made us discuss the idea of being able to talk back and forth at that time, but DocJohn says go to PM and then agree to meet in chat. Some things he just isn't up to speed on sigh how it would be SOOO neat to have that ability to say hi when we see someone on line we "know" too...
I often check who's online but I don't do it to be nosy, but if I've sent someone a PM or want to catch someone for chat... if I'm worried about another member... often we come in (as members) and don't post, don't go to chat and no one knows we're still breathing... checking online just helps us keep the anxiety level down.
(Yes, I do use the "notify when read" option when I send some PMs.)