I sometimes forget what tasks I have added a note to.
I'm not sure how it could be pulled off unobtrusively, but it would be nice if there was some kind of visual cue to folded up tasks that have a note attached.
It sounds like you are using the multi-line format. If you use the grid format, you can see the note icon. I'll add it to our to-do list to try to make the presence of a note visible for multi-line users.