Yes I agree. I would really like to be able to add Comments, and see comments, freely across the app. In fact I have communicated directly with @mdubakov that I would even like to be able to have a comment automatically pick up a reference to a related entity, if it could be surfaced in say Collections.
Here is an example from Coda where you can see with the right-click menu you can comment straight to an entity without opening it, is this what you mean?
I also think this is related to this request, another good use of comments:
Thanks!