My app is not running in the ticket editor tab, it is in the new ticket sidebar.
There is no documentation in:

https://developer.zendesk.com/api-reference/apps/apps-support-api/ticket_sidebar/#comment-object

that I can find explaining that this is feature is missing from New agent workspace, on the contrary it says:

"In the Zendesk Agent Workspace, setting comment.text during a chat conversation auto-transpiles rich text into plain text (Markdown syntax) in the chat editor."

Have I understood something incorrectly?