Back at home, his own reputation would tend to be enough to vouch for someone else's reputation, but this isn't home and she doesn't know him well enough for that yet. Of course his reputation at home is partly due to his association with the Starks, but he's also done plenty to earn it on his own.

"It's not just me. He was highly regarded throughout the North. All of the Starks are. There's a Mormont named after Lyanna." She'd been the first to call him a Stark, to give him a place to belong in the North, and that was enough for him. "Not just within the North, either. Stannis Baratheon once told me how honorable he thought Ned was." Though he doesn't expect the word of a Baratheon is enough for her either.

"He kept me safe. Protected me, raised me as part of his family, when he didn't have to." He can't imagine Ned Stark doing anything other than protecting his sister's son though, whether she had asked it of him or not. He doesn't know what Ned's opinion on the matter had been, but he'd raised his nephew without complaining. "Not everyone would have done that, and if that gives me bias, then so be it."

One thing that Starks are is loyal.