I suspect common sense is used more than this forum would acknowledge on this issue, only on saturday I sat in the Jumpseat for the entire flight whilst flying a domestic route in South Africa. Ths skipper judge me to be of no threat to the safety of his aircraft and invited me up after a discussion about the pro's and cons of flight training in South Africa. When I asked him if this was strictly allowed his reply was who's going to know?
It is not the first time I've jumpseated since 9-11.
Anyway there you go, sounds to me like this guy was the sort of bloke you'd like to know - in a world of jobsworths.