Character compatibility is the set of animations for weapons that a particular player model has that basically decide what weapons that model can wield. Most of these animations are not used, however can be tested using modding. This does not include swapping the actual character models - for example, swapping Marine character models with Grunts allows Grunts to throw Frag Grenades. This only applies to swapping weapons, otherwise everyone could use every weapon. This information is not absolutely guaranteed to be accurate, as not all combinations have been tested, some have been assumed based on the results of other weapon wield tests.