Formally filing some issues which were previously noted parenthetically in JENKINS-22472:
SetBuildResultCommand checks Item.BUILD; I would have expected Run.UPDATE. And SetBuildParameterCommand does no check at all.
getCurrentlyBuilding does not even check Run.isBuilding, so this could even be used to mangle a completed build's state, such as parameters via SetBuildParameterCommand. (SetBuildResultCommand would not work on a finished build because of checks inside Run.setResult.)