I could see a case for an option to give category mods that power, too. We host events, so during our conference we may temporarily give Marketing the ability to be a category moderator where that event is. In the event that there is a user that needs dealt with, I’d want them to be able to silence them sitewide if needed, to protect the whole site.
But I wouldn’t want them to have the ability to moderate other things outside of that category.