Detecting "quick falls" in signal
The circuit you show is also called a "data slicer" and is used effectively in extracting data from the output of an FM demodulated signal used by several not-so-cheap 434 MHz RF transceiver circuits you see quite often.



Yours is a variation but probably doesn't need R102 because R101 will perform that function as far as I can tell but there's no harm including it I guess. I'd try it as shown above or one of the many variations I have linked. Simulation is your big friend here.