Well there is a difference between trolling and grieving, Grievers ruin the game, Reach had a lot of those.
Trolling back is one of the things I enjoy, especially the younger trollers, the best one I encountered was a kid screaming that we should be nice to him since it was his birthday, nobody cared and ignored him, so he got mad, started cursing and saying he would call the cops on us and tell them that we offered him and I kid you not , offered him a syringe of marihuanna.
So I acted all scared, because I didn't want the cops after me, so I asked him to forgive me for ignoring his birthday, upon which he said: "Fine I will not call the cops since it is my birthday, but do not ignore me again or else I will still call them." Then I hit him with a warthog, he got mad, he rage quited. Few minutes later I got an XBL message from him pretending to be a cop. I never laugh so hard.