When I was implementing this feature in my app I decided against both of these approaches and instead piggybacked on less icon-friendly terminology that everyon

When I was implementing this feature in my app I decided against both of these approaches and instead piggybacked on less icon-friendly terminology that everyone understands: Remember this. I felt that favoriting and starring implied that you liked an item, and flagging seemed to have a slightly negative connotation (think soccer). I wanted a term that didn't imply that you liked or disliked an item, just that you wanted to remember it for later.