According to forum poster Fiametta, who kindly sent me the translations for the scenes, Jin says to Sun, "Even you won't believe me?" Ah, man, they teach the actors all sorts of things in the year 2525. Sun doesn't say anything. Michael turns to Sun and demands to know what he said. Jin then speaks to him; he says, "It wasn't me. Not me. Do you get it? It was already burning when I got there. I was burnt when I went to stop the fire." Naturally, Michael concludes that what Jin is saying is, "Yeah, I burned it. And danced to the rhythm of your screams. Because I have it in for you." And he responds accordingly, i.e. goes thermonuclear and invites Jin to say it again. Jin does: "Michael, it wasn't me." And Michael proves that Korean is neither his second language, nor his tenth, by rushing over to Jin and delivering a punch that knocks him to his knees.
Jack goes to break it up, and Sawyer and Sayid run interference. Sawyer's all, "One fight at a time." Oh, now he's the voice of reason? Or is this just part of his plan to woo Sayid away from the other hot blonde on the island? Sayid's all, "Hey. What could be more fair than a fight predicated on a total lack of mutual communication skills?" Nice. Walt, whom everyone including Michael seems to have forgotten about, is standing on the beach practically trembling with...something.
Jin struggles to his feet. Around a mouthful of blood, he repeats that he didn't do it. Michael interprets this to mean that Jin's now saying, "If I thought I could have gotten away with it, I would have roasted a fish in the coals. And eaten it while you sobbed! Without offering you any!" So he responds by knocking Jin down with another punch. Everyone winces and looks dismayed and does approximately jack and/or squat. Jin's on his knees, struggling to get up. Sun's looking horrified. Jack's looking impotently furious that he doesn't have a solution to this problem. Walt looks appalled. Jin wavers on his feet and repeats that he didn't do it, and was trying to put out the fire when he got burned. Michael's drawing back his fist for a monster punch, and Sun screams, in English, "Stop it! Leave him alone!"
Cut to Jin's bloodied face: he's wearing an expression like, "I've been beaten so badly, I'm now hallucinating that my wife can speak the same gibberish as these people!" Everyone else merely has the "Whuh? Did I...oh, crap, I hope I didn't say anything embarrassing around her before" look. Sun glares at all of them and says in the tones of someone who is watching a bridge burn while she holds the torch in her hand, "He didn't burn your raft." Jin now looks like he's thinking, "You couldn't have pointed this out sooner?"