Victor spends a good chunk of text talking about how much he hates Ferdinand, why he hates Ferdinand, and why the man is a waste of space. Yes, this characterizes Ferdinand in a direct way, but it characterizes Victor in an indirect way. Check out the foil that these characters form in Shmoop’s Character Role ID, and you’ll see what we’re talking about.
Ferdinand and Segur’s dialogue gives you a sense of just what sort of jerks they really are. Just look at Ferdinand’s rant against criticism, or Segur’s pretentious contributions – in French – to the inane conversation over lunch. We also thought it was interesting that Victor has very little direct dialogue. In fact, he only speaks twice to Nina, first to say, "Let me see, where did we last meet" and later to ask, "Look here—what if I love you?" and retract it with, "Never mind, I was only joking." Nearly ALL of "Spring in Fialta" is about his interactions with her. That we get to see so little of it in scene and that we get most of it in summary reminds us of the limitations: we’re getting this information through Victor, and through Victor only. We don’t see it as it happens – we see it as he remembers it. And the text’s limited dialogue makes sure we know that.