I just had a similar idea to what others are saying. It seemed so obvious I thought it might already be implemented, but since I couldn't find it, I came to the forum only to find others had already suggested the idea.

I'd love to be able to add player names to a hit list which will make the stat tracker notify me when they appear on my kill feed. It would be nice to be able to keep track of certain players without having to stare at the kill feed in game. Whether they are enemies you enjoy fighting, or just someone that decided to send you rage tells during a fight, it would be nice to be able to keep track of them without adding them to your friends list. If you want to get fancy, add a field in the tracker target list for the user to add a description of the player and why they were added to the target list.