OF COURSE THAT SHIT IS POSSIBLE!!! Jeeze, a fighter chopping off two goblin heads at once with a wide arc of their signature weapon?! That is Dungeon World!
I like to remind everyone at the table that DW is a fictional game. We tell awesome heroic stories at the table. So if you want to narrate something cool into the story then go for it! Its never using a move first to shoehorn the story to match its mechanical expression.
In your example Ambayard, when the fighter said they gut two goblins at once with a sweeping arc of their blade I would have jumped up in excitement! Woo Fighter! That's AWESOME! That is just what the rules ask for! To do it do it, right? It sets up all sorts of author 'hooks' for both you and the other players to riff off. If they had said 'I hack and slash the goblins', I would have said 'sure, what do you do?' You want this sort of detail in the players descriptions :)
So then back to the rules.... Sounds like Hack and Slash right? 'When you attack an enemy in melee'.... You could be pedantic and point out it says 'enemy' not 'enemies', so no, you just attack just one of the goblins. (LAME - and castrates the players fun and goes against your principle of Give Every Monster Life)
You could strike a compromise and make a quick custom move on the spot. 'Sure! that sounds epic and heroic! If you deal damage, you divide it amongst both goblins, kay?' Note that on a miss or goblin attack in return, dealing damage to the fiighter is the waste of an amazing fictional opportunity!
Or you could go all superheroic 4e style. You say YES! to as much as you can, rewarding the player's authorship with your own. Taking their exposition, riffing off their story and making moves to suit and that make sense within the fiction. Use your principles in situations like this, that's what they are for!
Dig a little deeper first.... Talk about the action before the players roll the dice, perhaps embrace the fantastic, or ask questions and use the answers. (note that the Walking Eye Podcast has a very good example of just this sort of thing in the fight with the Guaraxx)
'OK Cool! Tell us how you set up your whirlwind attack!'
'I crouch low and swing my custom tulwar in a wicked figure eight, the hook catching the second goblin behind the ear and evicerating the first in a pool of gore!'
'Awesome! The goblins are taken aback at your full frontal assault, so if you hit you are able to deal your damage to both of them, no worries!'
On a near miss or miss though, you have so many fictional 'grabs' to propel the fiction now. The fighter could 'pop' their knee when they crouch, and be unable to rise, or their hook on the Tulwar catches the goblin and drags him into the wizard, interupting his incantation, or the goblins perform a comic 'leap' above the swishing blade as it scythes into the thief behind, breaking his poison bottles and spraying the contents all over the fighter. The goblins watching on learn from this encounter and prepare for the next by flinging a net over the fighter, or herding him into a small space. Whatever.
See how that works? Its not about arguing what is and isn't possible 'by the moves'. Its playing your character as a Fantasy hero and having the GM fill their lives with adventure!