This market has nothing to do with Fed liquidity. It's been driven by illiquidity. Almost every night for a month, the day's price has been set by a small number of transactions in the futures market at the least liquid time of night.

                                                                                          hourly view

The S&P is up double digits this month, however, most of the action occurred at night. Month-to-date, we’ve had just one day that traded more than 10 points on either side of unchanged and today was yet another gap that remained on that side of unchanged for the day.

...nobody should be under the perception that [commodity futures] can't go below zero...We've seen other commodities go below zero in the past...We have to do things to allow the market to go to a price [that] is reflecting the fundamentals of the product...The futures market worked to perfection...small retail investors...need to make sure they understand the rules... - CME

Why can’t wine prices go below zero ?

"In bull markets stocks don't go down on bad news."

 For the SP 500, today was the 9th day in the past 10 days, the day session gaped and remained on that side of unchanged. That has NEVER happened before. We've seen 8 of 10 but never 9 of 10. The interesting part is we've gone nowhere in the 10 days and are right in the middle of that range. 

"The market is the sum total of the wisdom and the ignorance of all of those who deal in it and we dare not argue with the market’s wisdom. If we learn nothing more than this we’ve learned much indeed."

US Futures Crude Oil Fall Below Zero For The First Time In History