The dodo should be extinct, or, musings about music notation

When I teach enharmonic modulation, I like to use an example from the third movement of Beethoven's Op. 10, No. 1 piano sonata. It's a sonata form in C minor, but the moment I have students analyze is an unexpectedly slow and dreamy coda in Db major (3:57). It's an amazing moment - a viio7 chord is arpeggiated slowly across four octaves, and is followed by a cadential 64 chord in C minor. (Side note: Wix does not support superscript and subscript in its text editor.) YES! It's an enharmonic pivot chord, becoming viio65/V in our home key; what a moment! I got this example from the Kostka/Payne textbook, and I've been using it off and on since around 2005. Whenever I show it, without fail, there is at least one student who is looking quizzically at the score, not paying any attention to the enharmonic modulation. They'll raise their hand slowly, and ask, "Dr. Boone? What is dodo?"

Ah yes, dodo. "DODO IS NOTHING! LOOK AT THIS INCREDIBLE MODULATION!" But by then I've lost the class, and we're all giggling at dodo. I'll show the entire excerpt, and it will make more sense:

Do you see the dodo in measure 111? It's the very unfortunate result of two simultaneous performance instructions; it's the moment that ritardando and calando collide. I'm quite finicky about notation, and I think that's because it's a large part of what I teach at the undergraduate level. My peers at institutions with graduate students are holding advanced seminars, but I honestly spend a lot of my time teaching students how to read music, and how to write music in a way that makes it easy for other people to read it. (Beaming! Spacing! Notehead size!) This isn't the only notational oddity in a music theory textbook (although it might be the funniest). At best, things like this can be distracting from the point of the example, but at worst, they can actually make the composer's intentions confusing and cause people to play something incorrect when they realize the example. Here's the same passage in the Heinrich Schenker edition, dodo-free: