Some of the social skills seem like they'd have combat uses. Specifically: Intimidator, Liar, Judge of Intent, and Persuader.
I picked these in order of how 'reasonable' they seem to me. I'll run them down one by one.
Intimidator: An intimidating presence in battle is very desirable. It increases the odds that an enemy will miss opportunities or even have their nerve broken entirely. I envision this manifesting in attacks against the intimidating dwarf - and possibly others adjacent to them? - being more likely to miss. After enough attacks have missed due to intimidation, attacks that would've otherwise hit, the game would start making morale checks on the frightened enemy to see if they flee. Wounds should diminish the Intimidator's effect, unless the Intimidator has gone Berserk, in which case they have no effect.
Judge of Intent: Fighters who are effective at reading the emotions and intentions of those around them are less likely to be taken in by tricks. Judge of Intent would allow the dwarf posessing it to ignore social skills used by their opponents as well as other trick/feint type abilities (if such were implemented). They're also slightly less likely to be hit in combat themselves. Berserk dwarves may or may not still benefit from this skill.
Liar: Cunning, dirty fighters can get the upper hand on enemies as well. Having a high liar stat should slightly improve accuracy and dodging. Liars are used to thinking on their feet and they use feints/tricks effectively on their enemies. Like with Intimidator, wounds should diminish this. Berserk dwarves wouldn't get any benefit from Liar.
Persuader: What is a highly skilled persuader doing in combat in the first place? Putting that question aside for the moment I was envisioning that after Master rank or so a tiny chance should be checked each action to see if they convince the enemy they're fighting to flee, with the chance increasing with skill improvements from level. Legendary Persuaders, and only legendary Persuaders, should have a similarly tiny chance of convincing their enemy to defect mid-battle.
It's hilarious to imagine Legendary Comedians in the battlefield but I doubt it would have impact on how the battle would flow. Perhaps such a character would improve the effective morale of their side? A laughing band of blood-spattered dwarves could be horrifying to face in battle itself. I can't decide what impact a high-level Comedian might have.
Flatterer, Conversationalist, and Negotiator seem similarly uncertain, but they're even more likely to be useless.
What does everyone think of the idea? Obviously, it's a low-priority thing, as I don't envision the effects should be all that strong. If it were implemented it'd be one of those 'dev team thinks of everything' ideas. As long as they're small enough not to be vastly detrimental to those who don't know them, I'm fond of obscure effects.