I suppose he can't really call her `Sir' anymore:) Maybe he was just a horrible judge of gender before. His lack of eyes must be at fault:)
The Nanoha Wiki implies that the fact that Bardiche refers to her as "sir" regardless of her gender isn't a factor of not knowing any better but rather a product of the era he comes from. I'm not sure when this was a thing, and I did some checking before responding to this and couldn't find any indication that "sir" was used for women (all I found was that either "dame" or "lady" was the proper female equivalent), so I'm not sure where the source of this implication comes from, and I probably wouldn't be able to ask the original editor who wrote that.
Bardiche... I'm older now, do you really think it's okay to keep wearing this uniform?