No because DJ isn't really a fire attack. Its based on heat from friction. Any fire is just a byproduct of the heat his leg is generating. Its why he can use it underwater.
My point being that it's possible that an Armament shield is protecting his body from the damage the heat would otherwise cause; that's what is implied with the Salamander technique.
Yes it is. It is an extreme stretch. All CoC is is intimidation and killing intent from other series. Its not a form of hypnotism. Haki is magical powers. CoO is just a manifestation of extreme intuition, combat-experience, empathy(in case hearing voices), and instinct. Its make for either to be used inadvertently.
…Nothing there gives a reason why a form of Armament Haki can't be used inadvertently. I didn't claim it was hypnotism, I'm not sure what you're trying to say.
You keep taking shortcuts in your logic and explanation. When does the shield get formed? Why would it get formed if its the first time Sanji is using DJ? He had the idea to use friction to burn through Jyabura's tekkai but also subconsciously knew his body couldn't deal with the heat so his willpower automatically created a shield of imaginary armor to protect him from his new ability? That is your argument?
It's a possibility, not saying it's certain, but it's a possibility that isn't completely improbably in my mind. We also don't know whether that was the first time Sanji used Diable Jambe, or if it was developed prior like Gear 2.
Also don't think Sanji accidentally used something Rayleigh literally had to beat into Luffy. That scene with sticks looked like a gag scene but it really was not.
If Luffy can use forms of Haki inadvertently I don't see an issue with Sanji being able to do the same. Luffy developed a personalized form of Armament Haki after realizing what it was; if he had "figured it out" and understood its uses sooner he would've been able to develop techniques much faster (Luffy's good at improvising combat-wise, but not really with things he doesn't understand).
I also don't see how Vanessa's post helps your argument. It says nothing of inadvertently using Haki only that Haki can be used more creatively than the generic uses we've seen from early examples. Creatively means your conscious of what you're doing. It isn't just happening the moment you need.
I think the point I was trying to make was more that different sub-types and -uses of both types of Haki exist; such that perhaps Zoro and Sanji developed their own personalized uses of Haki inadvertently from their strong willpower.
I'm not saying any of this is at all certain. But it's not impossible either.