Some people like mud fights or bird throwing fights or whatever, and that's great for them. Some people don't like it, and those people should be able to turn them off. It doesn't have to be an all or nothing thing, I've seen it done in LOTRO which is an older, clunkier game. A simple toggle would let people opt out of involuntary emotes and at the same time prevent them from being able to use them without retaliation, so nothing is gained or lost. And the only people who would be upset at not having their memento work on someone are the ones who were doing it to grief in the first place.