Fired up the search engine to look around for an explanation as to why, in this day and age, the New Yorker insists on using the diaeresis in words like "reëlection" and "coördinate". Turns out it's nothing exciting; they're just sticklers—see also this bit of awkwardness—but along the way I did manage to find the definitive history of the "heavy metal umlaut," which presumably has been passed around before, but I've never seen it. Best part: the n-umlaut, as seen in "This is Spinal Tap" is "only found in the Jacaltec language of Guatemala and in some orthographies of Malagasy."