Open the panel
Choose Comments on the right of the tab bar. An empty thread shows No comments yet. A dot on the button means there is activity to read.
Write
The compose field uses Write a comment…. Send from the button next to the field. You can attach a file to a comment from the paperclip control.
On shared Docs
Editors you granted can comment on the same Doc. Comments are not a public thread and are not a substitute for a share grant.
