Taking notes on keyword selections

If I want to take notes on a keyword selection I've made, how do I do that?

If I add a note, or change the file name it changes the original file and every keyword selection I've made. I just want to be able to say "this is about..."

Is there any way to do this?

Be sure to switch to list view in your event.
Then open the disclosure triangle next to your clip name, and you'll see the keywords you applied to this clip.
You are now able to fill the Notes column for each keyword.