If we wanted to do as little as possible to overcomplicate yesterday's Fed news, we might focus on the fact that the Fed took their greatest strides yet in adding a new dimension to their job description.  We're talking about the mention of "recent global economic and financial developments" putting downward pressure on inflation. 

The argument that this circuitously leads back to the Fed's inflation mandate is too much of a stretch.  If the Fed speculated on every threat to its mandates, they couldn't possibly function.  They must necessarily wait for actual trends in inflation and labor markets before acting.  It's not their job to speculate on the Chinese economy and its effects on domestic inflation and job growth.

Nevertheless, they've made it their job, and that can't help but create downward pressure on rates.  Why?  Because the global economy sucks!  Apart from the policy implications, there's an even more important tacit implication: The Fed is concerned enough by the global economy that they bent their rules in order to address it.  It's a clue, if you will, as to just how much of a concern the aforementioned 'suckiness' could be.

The rest of the world got its chance to consider that in the overnight session, and did the only logical thing it could: sold stocks and bought bonds.  And here we are with marginal additional gains in Treasuries and MBS.