Dignity, dignity, dignity. If you want a relic from a bygone age in Spain, you've found it in Fernando. Not that he's the oldest character; he's definitely younger than Anselmo and probably Primitivo. But he's so serious and concerned with "dignity," which for him amounts to serving ancient Spanish custom, that he seems like a one-man Antiques Road Show. Fernando's the only character who's bothered by bad language, but only because he thinks young ladies like Maria shouldn't have to hear obscenities. He doesn't like "rumors," or seem to put any stock in them, even when he should. He likes soup that he's had for forever, just because he's had it for forever.
No surprise Fernando is the comic relief of the book, though we're definitely laughing at him, never with him (since he never laughs). Pilar can't resist making fun of him, and even Robert Jordan calls him the "Cigar Store Indian" (not to his face, of course). Ironic that somebody whose paramount concern is dignity should be the laughingstock of his friends.
To be fair, Fernando's principled: he's more reluctant to kill Pablo than any of the rest, except Anselmo. And he's got the self-discipline which other folks, especially Rafael, lack.