As our first-person narrator, Jim Hawkins frequently gives us his observations about the character of the people around him. What's frustrating – both for us and, we assume, for Jim – is that his observations are often wrong. When Jim first sees Long John Silver, he assures us that he's a stand-up guy. And when he first sets eyes on Ben Gunn, he describes the poor fellow as appearing half man, half ape. He thinks that Ben Gunn's long years on the island have driven him nuts.
Yet in both of these cases of direct characterization, Jim is proved at least somewhat wrong: Long John Silver is brave, sure, but he's also a murdering fiend. And Ben Gunn isn't crazy, though it takes Doctor Livesey's perceptiveness to see how useful he can be to the good guys. To sum up, we gradually learn not to take what Jim says completely at face value – his direct characterization can't be trusted.
When you're a pirate, you're a pirate all the way, from your first shot of rum to your last dying day. As we discuss in our "Character Analysis" of both the pirate crew and Squire Trelawney's servants, occupation is a huge means of characterization in this novel. Check out "Characters" for more on this topic.
Pirates talk like pirates. They say things like, "avast!" and "belay there!" Gentlemen talk like gentlemen, saying "sir" and "you may" and other polite nothings. The only person who really evades this relatively rigid form of characterization is Long John Silver, who is as capable of giving a piratical "Shiver my timbers!" as he is of saying "[I have] come back to do my dooty [duty], sir" (33.42). Long John Silver can put on multiple faces, which is what makes him fascinating. It's as though he is aware of the fact that speech and occupation are characterization tools, and he deliberately plays with them so that different people will assess him differently.