Your answer is in the international Contract of Carriage.
http://www.delta.com/content/dam/delta-www/pdfs/legal/contract_of_carriage_intl.pdf
Bottom of page 57. Rule 116, Section E(2)(a).
Passengers making connections to the first available Delta flight departing from an intermediate point may reclaim their baggage at the intermediate point if the connection exceeds six hours, but is less than twelve hours. If the connection time exceeds twelve hours, the passenger must reclaim his baggage at the intermediate point.
If the connection exceeds six hours, it is your right to have the bag short-checked. This should end the discussion with any Delta employee who tries to tell you otherwise.