DISCLAIMER: This comment doesn't answer your question. Consider it an experimental comment.
Came across this while re-reading the SN FAQ (trying to make more sense of the reward system).
I'm not surprised that your question hasn't been answered. :) Like me, you've probably also since realized that it won't be answered. Not here, anyway. I've referred to it elsewhere as "an inside joke" when someone else asked what the cowboy hat was all about.
Glad to see I'm not the only one that wondered. With a current streak of 53 you must have figured it out, right?