Lanefan
Victoria Rules
It's rare, however, that a social interaction is going to have as direct and immediate influence on the health and-or functionality of your character as is combat.But you’re still pretending. Are all your players professional orators? For your players to replicate skilled court intrigue, all they need to be able to do is speak?
I can narrate my attack on the giant just as easily as I can narrate my attempt to persuade the guard to let me by. Both of these things could fail....why does one have rules to determine success or failure and the other does not?
Exactly. Stop here and we're all good.I think that not having any social based mechanics at all leaves everything up to choice. The player decides how their character feels about everything. The GM decides how the NPCs react to the PCs.

And for the first two, it's very possible to put ourselves in such frames of mind while in character. The character is overcome by desire, and his rationality goes out the window. The character is provoked to anger and so she says things she shouldn't, and is likely to regret (or be made to regret) later.But what about when someone feels something without choosing to?
We’ve all found ourselves provoked to anger. Or overcome by desire. Or stricken with fear.
For the third, 'fear' is in many systems a mechanical condition externally imposed by any number of possible sources.
There's already loads of mechanics that potentially take away control. Fear is one. Charm and all its associated offspring are others. Emotion-affecting spells and magic are yet others. Possession is another, and-or curse.Sometimes these things are not choices. Having a game mechanic that may help replicate that lack of total control over ourselves seems like a potentially powerful tool for a game.
A game mechanic that allows Joe's character Halfdan to provoke my character to anger (or some other strong emotion), overriding any other in-character response I might have had to whatever Halfdan is doing or saying, is for many reasons probably a bad idea particularly for those who don't like PvP in their games. (hell, PCs charming other PCs is already bad enough!)

But here's the rub: if PC-PC relations are determined by their players then in the interest of consistency PC-NPC relations must as far as possible also work this way, and RAW be damned.