Yeah, likewise. I often read late at night and I'm usually a bit tired and not really in the mood to make articulate comments, so it's either say nothing or say something inane like "Good. Like. Thanks." The kudos function helps get that point across easier.

I might comment there more if I had an actual AO3 account... but after trying for months and getting deleted from the sign up waiting list twice, I've kind of given up.