Well, we probably have different editions of the novel, but the narrator speaks of Jim early on, saying, "no disappointments have been severe enough to chill his naturally romantic and ardent disposition." That's on page 712 of my edition; it shows how much the narrator sees him as romantic. I would say the way the two keep talking about a girl from long ago who meant "the whole adventure of their childhood," is another: both the fact that they keep talking about her, and that a person seems to sum up childhood that way. (That's also page 712 of my edition.) Of course, Jim writing about her is another example.