I don't use kudos. If I like a story enough to finish it I will leave a comment. (ETA: And include it in my weekly rec post.) It might be just one or two words or it might be several paragraphs, all depending on how much I liked it and how well my brain-to-English translator is working at the moment. I trained myself to always leave comments when I became active in fanfic fandom back in 2004/2005 so only leaving kudos would feel like I'm cheating.