Nice words, but here’s the irony. The loya jirga itself is kind of parallel government, unelected by the people, selected and invited by Karzai, which potentially undermines the authority of Afghanistan’s duly elected legislative institution, the parliament. Afghanistan has had loya jirgas longer than it has had parliamentary democracy, of course, and there is no indication that Karzai is deliberately making an end run around his critics in the Afghan Parliament.
Given that the "Traditional Loya Jirga" lacks formal requirements to assume constitutional powers, its main authority is political. Therefore, its success will depend on whether President Karzai has chosen members that truly represent diverse constituencies and limit themselves to political outcomes. If instead the delegates are seen as exclusive of key interest groups and attempt to make legally binding decisions that could not be approved otherwise, this Loya Jirga will represent a significant setback for Afghan democracy and could foment greater conflict, rather than pushing forward the priority of peace.