Kudos definitely has led to me commenting more in general! If I've left a trail of kudos behind me, I feel a lot less awkward about jumping in to comment on the one story that I actually have something substantive to say about and enough time to sit down and comment - I don't get all stressed about "what if they think I hate all their other stories because I only commented on this one?" and things like that, which lead to me never commenting at all.