If you need to write comments for a particular clip, document, photo or other item you see on a drive in a Mac finder window, it requires opening the dialog box.
Select the clip, then command>I which opens the dialog box.
There you can add tags, comments and look at the permissions for the clip. You can also select a different default video player or Open With item (you can also do that system wide in
System Preferences). You can't just click on the comments box in the menu bar.