Calling out a line from the above README instructions that Jenne pointed me to that confirms my suspicions that the *reason* the bad FF filter's high Q feature showed up at 102.128888 Hz, right next to the 102.13 Hz calibration line:
    "IFO in Commissioning mode with Calibration Lines off (to avoid artifacts like in alog#72537)."

in other words -- go to NLN_CAL_MEAS to turn off all calibration lines before taking active measurements that inform any LSC feed forward filter design.

Elenna says the same thing -- quoting the paragraph from LHO:72537 later added in edit:

How can we avoid this problem in the future? This feature is likely an artifact of running the injection to measure the feedforward with the calibration lines on, so a spurious feature right at the calibration line appeared in the fit. Since it is so narrow, it required incredibly fine resolution to see it in the plot. For example, Gabriele and I had to bode plot in foton from 100 to 105 Hz with 10000 points to see the feature. However, this feature is incredibly evident just by inspecting the zpk of the filter, especially if you use the "mag/Q" of foton and look for the poles and zeros with a Q of 3e5 (!!). If we ensure to both run the feedforward injection with cal lines off and/or do a better job of checking our work after we produce a fit, we can avoid this problem.