What you saying is that an offline jumpseater, with no affiliation to Delta, should get on a flight when Delta paying passengers cannot otherwise get on? If we have pulled all the strings and are maxed out on weight, due to whatever restriction, then we cannot add another person, revenue, nonrevenue, or offline jumpseater. The Delta jumpseat is specifically protected from payload optimization for Delta pilots and flight attendants only, and in that situation a Delta JS'er will cause the removal of an additional revenue passenger in order to be accomodated. Delta will not bump a revenue passenger to protect an offline jumpseater, no matter how many rants they make on the internet.

If there is weight available after all Delta revenue and Delta nonrevenue passengers have gotten seats, then absolutely an offline jumpseater gets a seat. If this situation happened where weight was available and a JS'er was left behind then that was not done properly. And it is not necessarily gross weight that is restrictive. Many times there are takeoff/climb restrictions due to terrain/wind/MEL/landing weight/alternate fuel/etc that limit takeoff weight to well below gross.