YouTube is running a new experiment that hides the dislike count on videos, effectively rendering it useless as a gauge for viewers as to how much others don't like a video.
A tweet from the official YouTube account explains that, "In response to creator feedback around well-being and targeted dislike campaigns, we're testing a few new designs that don't show the public dislike count. If you're part of this small experiment, you might spot one of these designs in the coming weeks." The tweet includes an image showing the Dislike icon without a count underneath, as shown in the image above.
A follow-up tweet makes it clear that creators will, "still be able to see the exact number of likes and dislikes in YouTube Studio. For viewers, if you're in the experiment, you can still like or dislike a video to share feedback with creators and help tune the recommendations you see on YouTube."
YouTube is attempting to discourage targeted dislike campaigns, which sees videos posted by a creator or channel receive a huge influx of dislikes. This can happen because a creator does something that upsets a certain individual with influence or a community which then responds en masse. Hiding the dislike count doesn't stop this from happening, but only the creator or channel owner will know it happened.
As this is just an experiment, there's certainly no guarantee it will become a permanent feature. YouTube could drop it, or extend it further and start hiding the like count, too, which seems unlikely. It also seems unlikely hiding the dislike count will stop targeted dislike campaigns. Those same campaigns would probably just use the comments section as an alternative way to publicly show they are angry or upset with a creator.