I do something similar in that I have filter in my Gmail which automatically adds labels to all the feedback I get on AO3, and on a quick look, I seem to have gotten 400+ kudos (in addition to comments) since kudos was introduced. No way would I have gotten 400 extra comments if the kudos hadn't existed, especially since my main writing fandom during that time has been The Mentalist, which is almost non-existent outside fanfiction.net.