Good point, Nick.  That may be the common denominator here.  By that, I take it that you mean our MIDI monitors are displaying 'ghost' MIDI messages, and the spurious messages themselves are generated 'in-the-(Win)box'.  Interesting dilemma here.   Now to get some of our Apple-based members to chime in.

I have an old Roland MC-50 sequencer that I may be able to kick-start.  It has a rudimentary MIDI monitor (I believe it displays by Command Set, not individual message type).  Or use it to record encoder moves straight out of the PitchFactor, and see what pops up (if anything).

That might satisfy my curiosity.  No matter where this is generated, I'd like to find out a little more about it.  I'm still on the fence on how deeply this kind of thing would impact me.