YouTube Originals are original series, movies, and events from YouTube. To understand who can view YouTube Originals, and when, read more here.
Comments on YouTube Originals are only visible to you if you have access to the full video. This means comments on YouTube Originals are accessible to all YouTube Premium and YouTube TV subscribers, who get ad-free access to all the available episodes of YouTube Originals. There may also be periods of time where YouTube Originals are accessible to all users for viewing, with ads. During these periods, any user who is watching the ad-supported version of a YouTube Original can view the existing comments and add their own comments.
Once the ad-supported viewing window is closed, viewers without a YouTube Premium membership will no longer have the ability to view the comments, or add additional comments on YouTube Originals. However, you can still view your own comments and have the option of deleting them by visiting your comment history.