Watching a draft and firing off changes one at a time is slow. Comments let you note everything as you watch, then hand the whole list to chat and get one revised draft back.

Every comment also becomes a marker on the timeline, so you can see where your notes fall across the whole edit.

When your notes are done, click [Send comments to chat]. Chat reads the whole list, proposes an edit plan covering every comment, and waits for you to confirm before it builds a new draft.

Comments work for structural changes: assembly, storyline, cuts, pacing, and camera switches.

For audio levels, color, effects, and captions, it is usually quicker to work directly: use the Adjust tab, the Effects app, and the Captions app.

Comments attach to a draft, so you need a draft open in the timeline. If a synced timeline tab is open instead, the comment box is turned off and the panel shows "Create a draft to leave comments." Switch to a draft tab. Also check that the playhead is on a clip in the draft.

You can, but the point of comments is to batch them. Chat handles the whole list in one plan, which usually gives a more coherent result than a run of separate requests.

No. Chat creates a new draft with the changes applied, so the one you commented on stays as it was.