Bill didn't say the character was implausible, just that he was useless. That social level is precisely that which makes him plausible (somewhat plausible -- a mere knight is IMO a tad low, socially speaking, for being THAT incompetent :devil

. As the old Imperial Navy aphorism (that I've made up myself) has it
"To get ahead in the Navy, you have to be either good or noble".
Incidentally, I don't recall many officers in Patrick O'Brien's books that had been promoted FAR beyond their competence; in a shooting war, incompetence tends to be self-correcting.
Hans