Curious. That means that both of our guesses about how MathJax is scoping labels must be wrong. If the scope were global (as I had guessed), we'd see the "multiply defined" error, and if the scope were restricted to individual answers (as you had guessed), then we'd see rendered math instead of source.

@LSpice: does the last equation in my answer look correct to you, or do you see the underlying LaTeX source (as I do)?

Huh, the "global collision example" I added at the end doesn't produce the behavior I expected. I thought it'd give me a red box with the text Label '*' multiply defined, but instead I see a white box with the source in it.

Thanks for organizing Gerhard! I'd like to attend some event in the Bay Area. How do I determine if I'm part of the overflow?

Thanks for organizing Alec! Should people do anything special to let you know they're coming?