Major Description
For example, if include the commandlog module, this has a mixin Object_recentCommands, which (of course) is intended to be contributed to all objects.
It turns out that it is also (seemingly) contributed to mixin objects, which doesn't make much sense, but there you go.
And then, with the new metamodel validation that requires that a mixin's action method matches that declared (typically "act"), we find that the contributed action's method - ie "recentCommands" - falls foul of this.
I don't think that the metamodel validation is at fault (though it might be useful to be able to disable) ... but it's clearly pretty weird for us to contribute actions to mixins.
