I know they were torn up and missing a side torso but they still had a big gun and ammo. Even out of ammo for the big guns I would think any clan warrior would stick around with the lasers to try to make a glorious last stand. Heck even with all weapons gone, I would start to think about making physical attacks (What? Can your codex really get worse?) or trying to overload my engine.
What situations can you think of that might cause a warrior in a Hunchback IIC to actually retreat?
I think it was in
Mechwarrior's Guide to the Clans for Mechwarrior/Battletech RPG 3rd edition that covered this situation well (in my mind at least). From what I remember, it essentially explained that a Clan warrior's personal honour and their Clan's honour aren't always aligned, and when they clash the warrior has to decide if they'll sacrifice their own honour to preserve their Clan's- which was resolved by making a roll.
A freeborn in a Hunchback IIc during the height of Operation Revival who's s taken down an Inner Sphere assault lance single handed will probably succeed at the roll easily and stride off the battlefield when their Star Commander orders them to retreat to ensure they're ready for the next invasion operation.
A trueborn solahma warrior who failed to prove themselves during the invasion and is now stuck in a Hunchback IIc doing garrison duty during the fifteen year truce with this fight being their last chance to die in combat is likely to face a
much more difficult role- even if they are fully aware their unit is held together by spit and duct tape and their unit can't afford to lose any 'mechs to isorla.
Modifiers would range from high (having no kills during the fight, fighting I.S 3025 units, pitted against dezgra enemies) to neutral or negative (having several kills, fighting another Clan, offered Hegira)
Regarding your scenario, it sounds like the Hunchback
should retreat. I'm not sure it would though- and even if its warrior was willing to retreat, you can also have the
Star Commander grappling with allow the Hunchback to retreat or ordering it to stay in the fight, because the Star Commander's personal honour may take a hit if their star loses the trial too.
It's unfortunate that I haven't seen much of this in fiction though. I think there's a lot more to the Clans than "Honour Rules Level 1 - 4" as a way to try and balance games between Clan and Inner Sphere forces.