Jon’s arc has an interesting structure. At its midpoint, he makes the decision to send Mance Rayder to save his sister, at enormous risk to the Watch. Only at the arc’s end does Martin reveal the consequence of this decision — the Pink Letter, which causes Jon’s downfall.
But between the Mance Mission and its consequence, we have an extended interim where Jon runs the Wall as he sees fit. Overall, Jon demonstrates extraordinarily competent and downright visionary leadership. He shows himself willing to modernize the Watch by granting favored positions to the wildling Leathers and the former boy whore Satin. He fortifies many of the Watch’s abandoned castles and makes various other important practical preparations to face the Others. He wins a crucial loan from the Iron Banker. Most importantly, he seeks out and achieves a peace with Tormund’s wildlings, both removing a dangerous threat and multiplying the Watch’s strength severalfold. The chapter where the 3,000 wildlings cross, to be integrated in the community on this side of the Wall, is a remarkable achievement that marks the pinnacle of Jon’s leadership. It will surely be a difficult adjustment, with much work remaining to be done, but compared to the Watch’s position in ASOS, Jon has clearly made enormous gains.
The catch is that, as he’s doing all this, he is increasingly choosing to risk all those gains, because of his heroic desire to help individuals in danger.
Interspersed with the above, Jon faces two new thorny moral dilemmas about whether he should use his power to protect innocent life. First, Alys Karstark arrives at the Wall seeking to be saved from her uncle. Second, the situation of the Hardhome refugees becomes increasingly dire. In both of these cases, rather than stand aside and accept that he cannot jeopardize the larger struggle with these interventions, Jon chooses to take on immense risks to help these individuals.
The Pink Letter cuts off Jon’s arc before these new gambles of Jon’s fully play out. But I believe Martin has included them for a reason — to show how Jon is still driven by the hero’s instinct — his “noble heart” — to take great risks, and that this is very much his Achilles’ heel as a leader. When an innocent is in danger, and Jon thinks he might have the power to save that person, he will use it, even if doing so could be very dangerous for the Watch. And, as he piles risk upon risk, he makes his eventual demise and failure more and more certain.