Comments and chapters will all appear as text annotations in live time. Watch this video for a demonstration:
Comments: Video owners can use comments for adding an afterthought, clarification, or an external link. As long as they are enabled, they are viewable to anyone watching the video.
The video owner and any viewers linked to the same organization as the owner can leave a comment. To enable commenting for viewers, the owner should check the setting under Permissions. Comments are intended to be interactive. Use them to ask your viewers questions and allow them to respond back with their own comment.
Chapters: Only the owner of the video can add chapters. Chapters are useful for marking different sections of the video, that way viewers can easily jump to the section they would like to watch.