After I threw the bike on the workstand, didn't take long see what's up. Please note the chain about to separate, masterlink pin poking out from the side plate. Yikes. That could have been ugly, if snapped during a sprint or powering up a hill while standing. The chain is also twisted a bit as well. I don't know if this occurred while the hanger busted, or somehow caused the whole mess, or even during test riding after installing the new derailleur and hanger. Weird chain of events - pun intended. In any case, the chain is toast.
I already had a new Ultegra chain on the workbench. Let's see how far the worn chain "stretched" in 9500 miles, compared to a new chain. How does a chain stretch? As the many pins and rollers wear, they develop more play, increasing the length of the chain. Here you can see the pins of both chains look fairly even at this point.
By the end of the chain - not so cool, eh? The worn (dirty) chain on the bottom is few millimeters longer. As you can see, the pins no longer line up. The cassette and chainrings have also worn to match the chain. A new chain added to the mix is a recipe for headaches.