I think all of the above are important. I can't decide which is most important though :p
Meaningful comments. And by that I don't mean "Awesome!! I love it! Write more!!!" I really love detailed comments that really tell you why the person loved the story, and basically proves that they actually read it.
Comments, so they can improve, and reads, for confidence.
Comments. Always. It's that comment that says what someone liked or disliked about it(with disliking things that can be improved, of course). My heart sinks every time I see the comment notification and then get a comment saying, "it's good. i like it." It's just so disappointing and it breaks my heart a little bit every time. I always just feel so good when I see that comment notification and get a quality comment. That makes my day.
I agree with NeverForget. I enjoy comments that aren't just a "Good story! Keep going!". But something that really encourages me to keep writing the story. Or someone who gives me advice on how to make the story better. And I just love it when I see a that I have a comment in my inbox!
The comments, everyone I'm sure wants their story to be read and enjoyed, to have all their hard work paid off. Heck I've seen rants about not having comments, that's how important they are, plus its the joy of seeing " Comment on your Quiz " in your inbox that's almost accomplishment. Besides, idk about you guys, but I hardly look at the ratings or number of reads.
Comments- not just a simple: "I like it! Keep going! :)"
That is encouraging, but it doesn't really tell the writer what you liked about the story, their writing, and what they could do to make it better. (I'm going to remember this the next time I read a quibblo story ahaha.)