What about markers with two (or more) heads?
My idea is this: set a marker and it looks like we're used to, but you can pull the head down to the track or item you want and enter a comment to and if pulling down, a new head is created at the top (if you want). The upper head of this, call it "multihead-marker" or whatever, could have a different shape or color to indicate that it is one of these, so you can see in the ruler "there is something" even if you can't see all tracks of your project.
Just an idea.
-Data
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