Let's start in no particular order with peoples (deliberately negative) adjectives for her.
Quiet, soft spoken. - I would choose to say careful, thoughtful and laconic. She doesn't fill the air with pointless sound and fury and giggles. She's like a calm lake with much going on below the surface instead of a frenzy of activity at the top with nothing beneath at all. I think this is fairly appealing to men.
Submissive, Hopelessly Devoted - This seems like it comes directly from some women's studies class. This isn't how I see Hinata at all. She's quiet, yes, shy yes, but in her own quiet way she's rebelling against her father, her clan, and looking to Naruto as a role model for that rebellion. He inspires her to push herself in her own direction rather than that society demands of her. She's also someone who frankly, on her own, probably would never even be a Shinobi but is being pushed into it by a very cruel father. I'm not sure, 'showing that you care' equals 'submissive' except in the minds of radical feminists.
tea making - Um. This one sort of tips your hand. Code for 'domestic house frau.' I think learning how to make dragon swirlies around your hand and punch holes through walls stands out more as a Hinata trait than 'making tea.' I'm not really feeling this one.
'full figured' 'cute female' - Oh no Kishi managed to make a sexually appealing character! Alert N.O.W.! And please ignore the 587 shirtless Sasuke panels and borderline homoerotic content when writing your letter of complaint to them.
vacant-looking expression - Another tip of your hand. This is pure projection. Hinata seems like one of the more thoughtful characters in the manga, and has clearly been shown to be massively conflicted and interesting in her internal mental space. Maybe you're thinking about Ino?
who blushes and faints and rarely speaks much - The blushing and fainting is more comic relief, like the whole nose bleed thing. In manga, boys and girls are tragically inept at handling romance. Because I think most japanese boys and girls are just as bad? Hard to say. But this is like complaining about anvils dropping on people in Bugs Bunny cartoons. Its comedic license.
The fact this character is so overwhelmingly popular is proof of the persistent and pervasive sexist ideals that underpin our society. - The fact that you can't see why a cute and nerdy girl who tries her best but often fails and sees how cool the nerdy main character is... why you can't see why geeky manga readers would find this character appealing is just kind of sad. Sexist ideals. Look at any other manga for those sexist ideals you'll find plenty of vapid whores in spandex and bikinis if you want to look at the sexist ideals. This is just odd here.
rarely speaks much and only acts out when it's romantically appropriate to serve or impress her man - I think this is more Kishi's increasing failure as a writer and his lack of competent editors in part 2, and the fact that the Konoha 12 are basically irrelevant to the manga anymore. She does a hell of a lot in the fillers, let me tell you.
To me, she just seems like a male supremacist's ideal woman. - To me it seems like you're trying to smash one of the most complex female characters in the manga into a Stepford Wife model she doesn't belong in.
The fact that Kishi doesn't seem that into her makes him seem less sexist to me, - This seems like a fairly strange view of sexist. But alrighty. Personally I'm thinking Hinata is a fluke of Kishi's sexist writing. I'm not sure what he was going for, but either he or some editor managed to make a semi competent female character study in her. I find myself hoping she doesn't do much in Part 2 simply because Kishi's writing has gotten so amazingly bad and overtly sexist in part 2.
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