YouTube, with their official announcement, said the following:
Helping you connect with your fans is extremely important for you and for us. This includes replacing little-used features with better ones. Currently video responses have a click-through rate of .0004% -- in other words, only 4 out of every 1 million users who sees a video response clicks on it. So, on September 12 we’re going to retire this little-used feature as we work to develop more effective fan engagement tools for creators. The team is focused on enabling you to share video links in comments. Doing this in comments will let creators and viewers add more context to a video, and more context should drive more engagement.
YouTube recommends the use of hashtags and unique phrases in video uploads to make them searchable. Users can highlight videos as links in descriptions and in playlists. This emphasis on search is a push to focus on titles and descriptions and engagement through comments.
