How we cite our quotes:
I could now see that he was a white man like myself and that his features were even pleasing. His skin, wherever it was exposed, was burnt by the sun; even his lips were black, and his fair eyes looked quite startling in so dark a face. Of all the beggar-men that I had seen or fancied, he was the chief for raggedness. (15.9)
Jim is describing his first meeting with Ben Gunn, who is looking about as tattered and tragic as possible. Jim is incapable of judging Ben's appearance correctly because Ben is so far outside Jim's personal experience of people. This is one problem with judging by appearances: you can only do so when you have a wide range of experience to use as comparisons.
A moment afterwards [Doctor Livesey] had entered the block house and with one grim nod to me proceeded with his work among the sick. He seemed under no apprehension, though he must have known that his life, among these treacherous demons, depended on a hair; and he rattled on to his patients as if he were paying an ordinary professional visit in a quiet English family. His manner, I suppose, reacted on the men, for they behaved to him as if nothing had occurred, as if he were still ship's doctor and they still faithful hands before the mast. (30.13)
While Jim is Long John Silver's hostage, Doctor Livesey comes by to treat the sick pirates. He does this out of kindness, at risk to his own life. It seems believable that Doctor Livesey has a professional manner he can just fall into automatically, as though treating these pirates is like treating "a quiet English family." It's also interesting that one man's behavior can shape the behavior of those around him, further proof of Long John Silver's point that you have to be careful who you hang around with because they will rub off on you.
What a supper I had of it that night, with all my friends around me; and what a meal it was, with Ben Gunn's salted goat and some delicacies and a bottle of old wine from the Hispaniola. Never, I am sure, were people gayer or happier. And there was Silver, sitting back almost out of the firelight, but eating heartily, prompt to spring forward when anything was wanted, even joining quietly in our laughter--the same bland, polite, obsequious seaman of the voyage out. (33.44)
Long John Silver's "bland, polite" manner seems to be a bit like Doctor Livesey's professional behavior with the pirates: something he can switch on and off depending on the situation. But this leaves us wondering what's going on underneath that bland manner, a question Stevenson never answers.