I agree with the concept of LJ posts being a ping but I don't see them in quite the way you do. For me it's about writing on a topic of interest to me and seeing if anybody responds. If nobody does I don't feel any less real but I do feel more out of step with the world. If people do respond I feel less like an island and more like an isthmus (which is perfect because I don't want to be part of the continent).