You have to have a sponsor, though. That's why they're (su) and not (ex)
Well, looking at the entry for Exalted Feats in the BoED, you're right, even if that is a fucking stupid justification for it (the correct justification is, "These are supernatural powers, because no matter how much ass you kick, arrows swerving aside because you're just so nice is not something that can happen without magic."). Still, the thing is, the requirements for a Vow exist completely independently of a deity's code of conduct; you can adhere to one without adhering to the other, and you can gain Exalted feats from entities other than gods. "Have Vow of Poverty" is not a thing on any deity's code of conduct, even if "Follow all the rules in Vow of Poverty" is. Even if it were, you weren't granted Vow of Poverty by following the code of conduct, you just happen to be adhering to both; so while you're protected from the consequences of violating the code of conduct (losing access to class features dependent on adhering to it), you still suffer the consequences of violating Vow of Poverty (losing access to Vow of Poverty), because those restrictions exist in the feat independently of the deity's code of conduct, and Heretic of the Faith does NOT protect you from the consequences of violating a feat's code of conduct.
Put another way.
Let A = following your deity's code of conduct.
Let B = following Vow of Poverty's code of conduct.
Let C = keeping your class features dependent on obeying your deity.
Let D = keeping the benefits of Vow of Poverty.
Not A -> Not C
Not B -> Not D
Ordinarily, all B is within A, and all D is within C, so the second rule is unnecessary, even though it's still true. However, Heretic of the Faith deletes the first rule. It does nothing to the second, though, which continues to operate.
Yeah, I don't think Heretic of the Faith really works for VoP. It only protects you when you violate your deity's code of conduct. You don't lose VoP for breaking your deity's code of conduct unless you gained VoP BECAUSE you follow your deity's code of conduct. Even if the same action violates VoP and your deity's code of conduct, the two restrict you independently, so even though you can violate your deity's code of conduct with impunity, you cannot violate VoP's code with impunity.
Aren't exalted feats supernatural entirely because they're granted by a deity?
So you swear a vow to do X, and your deity gives you power because of that. How is that not power granted by following your deity's code of conduct?
Because that's just a fluff explanation. VoP has a list of rules you have to follow in order to benefit; your deity's code of conduct exists completely independently of the restrictions on VoP. Even if the same rules appear on one or the other. Besides, what would you do with an Exalted character who had no deity? I thought that exalted feats just came from your inherent purity and awesomeness, but were supernatural because they gave powers based on spiritual attributes (purity of heart, etc).
I mean, really, I don't see a real difference between saying, "My deity's fluff includes VoP's restrictions as part of its code of conduct, so if I'm protected from consequences of violating my deity's code of conduct, I'm protected from the consequences of violating VoP." and "My character's fluff includes being an in-game paladin (even if his character sheet says Cleric), so if I can quicken all my Paladin spells, I can quicken all the spells I cast."
All vows are sworn to a good deity or good cause, as per Scared vow. A vow sworn to a god is a person specific code of conduct.
Yes, it is a person-specific code of conduct, in exactly the same way that a Cleric who fights a lot is a paladin. Do Clerics need to start taking Battle Blessing? Besides, it's a code of conduct, sure, but it's not the deity's code of conduct; a deity's code of conduct applies equally to all its followers.