There was once a great Jedi. This great Jedi thought that he will be as supportive as possible. This Jedi buys push. This Jedi will do his or hers best to push the bad nades away to keep the teammates from harm's way. Sadly, this is not always so easy for our hero jedi; the nades can sometimes be devilishly tricky to push that even our great Jedi might once or twice push one into their teammates and make a big mess out of them. Usually teammates understand that the jedi only pushed the nade accidentally into them and are kind enough to press f2 to forgive the great Jedi. Now this is where the system truly punches the great Jedi into the groins. No matter how supportive our hero tries to be, he now has so many tk points that the great jedi is starting to second guess about pushing nades in the fear of hurting his teammates, inevitably leading to his own demise by tk points.
What can we learn about this tragedy of great Jedi the supportive? That something has to change. This is how I would change the system of punish, ignore and forgive:
Punish: Pretty simple, it will stay exactly the same
Forgive: not only does it not punish the player that team killed, but it also forgives the tk points that the finishing blow dealt
Ignore: Does not forgive the tk points that the finishing blow dealt, but neither does it give any extra punishment anymore