Eh, I'd argue that pretty much any definition of "master" that would apply in a wizard/familiar relationship is masculine. Most gender-neutral forms of the word are either adjectives or verbs; the only noun forms without a distinct masculine implication are highly specific (such as in chess) and not relevant to V.

Equally, I don't see how that constitutes any evidence of V actually being male. All it would mean is that Blackwing considers V to be male. In fact, even if Blackwing actually knew that V was male, it wouldn't mean anything unless we were told about it; for all we know, Blackwing's just making a guess.

Personally, I've always considered V to be male because his actions and mannerisms have generally been more stereotypically male, but that's really just my preconceptions at work. There's not really any evidence at all for either side of the debate, and since the author himself has explicitly said that there will never be any decisive evidence for either side, the argument seems a little pointless.

My only real beef is with the people who insist on using bizarre, made-up pronouns for V - just pick "he" or "she" or "they" and stick with it, guys.