Coming from a long-time lurker who's trying to become more active in commentary, I often enjoy stories immensely but usually find I've nothing of great weight or interest to add (as I see it) to the conversation and so avoid commenting entirely. This might be called "fear of having nothing to say"
I suppose it begs the question, to the writers, whether a simple "I enjoyed this story" or "thanks for posting" are appreciated as well as more in-depth comments devoted to literary analysis or constructive criticism. I will say that as someone who's written/performed in other arenas, I can understand the feeling of transmitting into deep space; the joy of creation is very important, but so is acknowledgement.