Interesting exchanges.

Fortunately I am a non-contributor this time. Simply posting an 'aside' .

If you have ever had business/Corporate dealings examined in a court of law you quickly find out that
the "law" is whatever the judge says that it is. Likewise for definitions .

I have the distinct feeling that the FAA will provide all the definition required and that the "comment period"
will prove of little use to the modeler.
IOW it is going to be as they say it is.

BUT, .......... we shall see .
I seriously doubt that "commercial use" is going to begin to cover what we consider normal model flying activities
including Demo flights, sponsorship etc.
Bill Hempel's flying in "The Aviator" clearly was commercial .
Quique's noon Demo was not .

However, Government agencies are well known for being tone deaf so take your pick of positions and lets see what is posted by the FAA.
Because THAT is when the toes will be pressed by the 800lb gorilla .