And moreover, I had gone to considerable length to present the Superhappy argument in the best possible light.

Hmm. I felt that while the Superhappy argument was presented in the best possible light, the Superhappy ending wasn't. The non-Superhappy ending was in two parts and contained all kinds of cool things, like the use of emergency flags to manipulate the local prediction markets and more insights into the personalities of the different characters. The Superhappy ending, on the other hand, was just one part and was basically just a pretty dull overview of how everybody considered humanity's future to be horrible.

To me, it felt like a pretty blatant statement of "this is the future that we don't want".