Good points, Gene.
I prefer the "keep it Active unless told it is unusable". This would be clarified by adding a checkbox for "Unusable". But, if we are going to keep courses Active unless Unuseable, then the checkbox is not necessary. What is necessary is to make sure measurers and certifiers understand what "Replaces" means.
We could accomplish that by adding "(old course is no longer usable as certified)", or something to that effect. This would also indicate to anyone accessing the cert on the USATF site that the old course is no longer usable as certified.
To me, the only other reason that someone could ask for a course to be made inactive is it part of the course is controlled (on private property) by the race, and the old course will no longer be used. In this case, no one else could use the course on the private property, so they could want the old course deactivated to avoid confusion.