When multiple items are checked it is possible to do bulk actions from the top menu, like add labels, or move items to folders. This makes sense, but some actions applied to an individual item, like adding a star, are also applied to all checked items. This can be a problem because items might be checked from a previous action and it isn't clear that adding a star to this particular item will also star all the other items at the same time. I don't know if there are other actions which work in this way, but I suggest that for any such actions, which are applied via the individual paper entry and not the top menu bar an alert box should come up and ask if the user wants to apply this action to all "X (number)" of papers or items.
See separate request for an "undo" feature.