Thank you for your reply.
So what is the purpose of having a comments field in the properties of a source clip when it seems to have no function?
Say I have a project file with two clips in the playlist -- what I called "source clips". Double clicking on the first clip from the playlist opens that clip in the "source" tab of the media player. The properties pane will now show the details such as metadata of that clip. Above that is a field for comments.
However, any comments written there on a clip from the playlist won't be saved. If after writing one, I subsequently double click on another clip, the comment will have disappeared when I revisit that annotated clip.
When I double click on a clip in the timeline and write a comment on it in the properties pane, this will be saved. So if I select the same clip from the timeline later, that comment will still be there.
Hopefully, this explanation cleared things up a bit