Upstart delivered blowout results, but the stock still fell. What gives?Followers of Palantir (PLTR 2.53%) will know that the company likes to use the Rule of 40 as a performance benchmark.This standard in the software industry means that a company should have a combined revenue growth rate and free cash flow margin, or a similar profitability measure, of at least 40 in order to be investable.Palantir Chief Executive Officer Alex Karp hasn't been shy about touting the company's strong performance based on t ...