The default for comments is set to off “if the primary artist doesn’t have an Official Artist Channel.” Once the channel’s comment setting is set to “Allow all comments” or “Hold potentially inappropriate comments for review,” you’ll be able to select Remove next to a comment on your Art Track to hide the comment. Update 12/24: YouTube now says you “can have comments shown on Art Tracks on your official channel.” Official Artist Channels in YouTube Studio can set (Settings > Channel status and features > Community > Defaults) comment preferences to “Allow all comments” or “Hold potentially inappropriate comments for review.”
The YouTube mobile apps and website have reopened comments on the auto-generated videos that are created for music.