For completeness, the baggage allowance of the longest leg applies to all other legs on all airlines (under the IATA MSC rule); so it doesn't matter that it is a QF codeshare or on a Oneworld airline; you';d get the same flyihng DL ATL-DFW connecting to QF if on the same ticket, for example. The QFF status benefits of extra baggage allowance are separate and generally honoured by AA on connecting flights but that wouldn't apply for non-Oneworld airlines in general (a few exceptions such as AS which has some special arrangements with QF, though it changes every few years). Quite a valuable benefit, I once had 100kg of baggage on AA connecting to QF and it was free thanks to status.