"Can I roll a big number on the dice" is not a compelling character moment.
I don't think this claim is true, actually - assuming it's meant to be a general proposition. (Of course we can all imagine circumstances in which "can I roll a big number" is not a compelling character moment - eg playing a 15th level AD&D PC who finds themself having to roll a saving throw against a 5d6 fireball. In most cases,
that will be a merely bookkeeping moment.)
I mean, suppose that my character is supposed to be the toughest guy around. Perhaps I (as my character) boast and swagger. Perhaps I am implacable. However I portray it, my portrayal conveys
not to be messed with.
And then a NPC (or even another PC) messes with me. And so the question arises, in play,
am I really so tough, so implacable, so not to be messed with? Or is it just an empty claim?
In every RPG that I can think of, this physical contest will be resolved via mechanics, not simply via talking it out. It may end up turning on whether a single roll is high or low. That wouldn't stop it being a compelling character moment.
Here's another example, one I already posted upthread I think, from my own BW play:
My PC is Thurgon, a warrior cleric type (heavy armour, Faithful to the Lord of Battle, Last Knight of the Iron Tower, etc). His companion is Aramina, a sorcerer. His ancestral estate, which he has not visited for 5 years, is Auxol.
At the start of the session, Thurgon had the following four Beliefs - The Lord of Battle will lead me to glory; I am a Knight of the Iron Tower, and by devotion and example I will lead the righteous to glorious victory; Harm and infamy will befall Auxol no more!; Aramina will need my protection - and three Instincts - When entering battle, always speak a prayer to the Lord of Battle; If an innocent is threatened, interpose myself; When camping, always ensure that the campfire is burning.
<snip>
The characters continued on, and soon arrived at Auxol,. The GM narrated the estate still being worked, but looking somewhat run-down compared to Thrugon's memories of it. An old, bowed woman greeted us - Xanthippe, looking much more than her 61 years. She welcomed Thurgon back, but chided him for having been away. And asked him not to leave again. The GM was getting ready to force a Duel of Wits on the point - ie that Thurgon should not leave again - when I tried a different approach. I'd already made a point of Thurgon having his arms on clear display as he rode through the countryside and the estate; now he raised his mace and shield to the heavens, and called on the Lord of Battle to bring strength back to his mother so that Auxol might be restored to its former greatness. This was a prayer for a Minor Miracle, obstacle 5. Thurgon has Faith 5 and I burned his last point of Persona to take it to 6 dice (the significance of this being that, without 1 Persona, you can't stop the effect of a mortal wound should one be suffered). With 6s being open-ended (ie auto-rolls), the expected success rate is 3/5, so that's 3.6 successes there. And I had a Fate point to reroll one failure, for an overall expected 4-ish successes. Against an obstacle of 5.
As it turned out, I finished up with 7 successes. So a beam of light shot down from the sky, and Xanthippe straightened up and greeted Thurgon again, but this time with vigour and readiness to restore Auxol. The GM accepted my proposition that this played out Thurgon's Belief that Harm and infamy will befall Auxol no more! (earning a Persona point). His new Belief is Xanthippe and I will liberate Auxol. He picked up a second Persona point for Embodiment ("Your roleplay (a performance or a decision) captures the mood of the table and drives the story onward").
Turning back to Aramina, I decided that this made an impact on her too: up until now she had been cynical and slightly bitter, but now she was genuinely inspired and determined: instead of never meeting the gaze of a stranger, her Instinct is to look strangers in the eyes and Assess. And rather than I don't need Thurgon's pity, her Belief is Thurgon and I will liberate Auxol. This earned a Persona point for Mouldbreaker ("If a situation brings your Beliefs, Instincts and Traits into conflict with a decision your PC must make, you play out your inner turmoil as you dramatically play against a Belief in a believable and engaging manner").
That was a compelling character moment. Thurgon fully committed - including paying his Will to Live - and his faith was rewarded.
Had it gone the other way, the effects on Thurgon and on Aramina would have obviously been very different, and as characters they would have developed in quite different ways.
Obviously it would be
possible to have a system in which the prayer is resolved by the player (as the PC) and the GM (as the deity) debating the PC's faith, the appropriateness of granting the prayer, etc. I can't see how that would make for a more compelling moment of play than what actually happened at my table.
And here's another series of example, less high stakes but still pretty intense at the time:
Thoth successfully performed Taxidermy - against Ob 5 - to preserve the corpse, with a roll good enough to carry over +1D advantage to the Death Art test but did not what to attempt the Ob 7 Death Art (with his Death Art 5) until he could be boosted by Blood Magic. And so he sent Aedhros out to find a victim
Aedhros had helped collect the corpse, and also helped with the Taxidermy (using his skill with Heart-seeker), but was unable to help with the Death Art. He was reasonably happy to now leave the workshop; and was no stranger to stealthy kidnappings in the dark. I told my friend (now GMing) that I wanted to use Stealthy, Inconspicuous and Knives to spring upon someone and force them, at knife point, to come with me to the workshop. He called for a linked test first, on Inconspicuous with Stealth FoRKed in. This succeeded, and Aedhros found a suitable place outside a house of ill-repute, ready to kidnap a lady of the night. When a victim appeared, Aedhros tried to force a Steel test (I think - my memory is a bit hazy) but whatever it was, it failed, and the intended victim went screaming into the night. Now there is word on the street of a knife-wielding assailant.
Aedhros's Beliefs are I will avenge the death of my spouse!, Thurandril will admit that I am right! and I will free Alicia and myself from the curse of Thoth!; and his Instincts are Never use Song of Soothing unless compelled to, Always repay hurt with hurt, and When my mind is elsewhere, quietly sing the elven lays. Having failed at the most basic task, and not knowing how to return to Thoth empty-handed, Aedhros wandered away from the docks, up into the wealthier parts of the city, to the home of the Elven Ambassador. As he sang the Elven lays to himself, I asked the GM for a test on Sing, to serve as a linked test to help in my next test to resist Thoth's bullying and depravity. The GM set my Spite of 5 as the obstacle, and I failed - a spend of a fate point only got me to 4 successes on 4 dice.
My singing attracted the attention of a guard, who had heard the word on the street, and didn't like the look of this rag-clothed Dark Elf. Aedhros has Circles 3 and a +1 reputation with the Etharchs, and so I rolled my 4 dice to see if an Etharch (whether Thurandril or one of his underlings or associates) would turn up here and now to tell the guards that I am right and they should not arrest me. But the test failed, and the only person to turn up was another guard to join the first in bundling me off. So I had to resort to the more mundane method of offering them 1D of loot to leave me alone. The GM accepted this, no test required.
Then, repaying hurt with hurt, Aedhros followed one of the guards - George, as we later learned he was called - who also happened to be the one with the loot. Aedhros ambushed him from the darkness, and took him at knife point back to the workshop, where Thoth subject him to the necessary "treatment"
Each of the rolls to kidnap someone, to sing, to meet an Etharch, and to kidnap George, was (for me, at least) a compelling character moment. The signing and the Circles both had the possibility of turning Aedhros away from his sordid world of service to a necromancer. But the final, successful kidnapping instead enmeshed him further into that world.