if I want you to know I am around, I will post in a topic...
Sometimes I accidentally post on a topic when I'm trying to lurk.
I just can't keep me big mouth shut.
Anyway, I say it is a silly idea. Things work as they are. You find where people are quite easily and if you're intertested in the discussion, you join in. If someone's not posting, their presence does not need to be known.