The 'Goats write lots of songs about doomed love (in fact, this has been a typical theme in songwriting for many years). They do it in a way that's unusual for songwriters. I've been listening to the Arcade Fire a lot lately. Some lyrics from a song of theirs on that very topic, Ocean of Noise:
Left in the morning
While you were fast asleep
To an ocean of violence
A world of empty streets
You got your reasons
Me I got mine
But all the reasons I gave were just lies
To buy myself some time
It's sort of introspective and self-deprecating, and you probably wouldn't say those words exactly to your (doomed) lover, but even so, the words could be re-arranged into something that could be a communication to said (doomed) lover. The details of the events that took place aren't really set out, because the (doomed) lover knows all them, it's an explanation of the speaker's feelings, and one with at least a bit of a motive.
The Mountain Goats, on the other hand (Tallahassee):
Twin-prop airplanes passing loudly overhead
Road to the airport: two lanes clear
Half the whole town gone for the summer
A terrible silence, coming down here
And you... you.
And from Oceanographer's Choice
But then you came in and we locked eyes
You kicked the ashtray over as we came toward eachother
Stubbed my cigarette out against the west wall
Quickly lit another
In the first he's establishing setting. In the second giving action. The mood and emotion are not just pounded in like a guy trying to earnestly plead his case to someone, they're embedded in the setting and in the events, like someone writing a novel. Although the speaker addresses his (doomed) lover with "you", he's telling a story to the audience more than anything else. It creates a distance between Darnielle and the speaker that lets the audience get much closer to the speaker. The songs are free to be more honest about the speaker's character. His first-person portrayals show all the flaws and warts of the characters, show their actions for what they are. He's not fishing for sympathy like so many songwriters; that's the honesty that makes his songs powerful. The feelings follow from the events and are free to be contradictory or ugly. This is why I don't agree with classifying the songs as earnest. Earnestness is (according to Wiktionary) "ardent in the pursuit of an object; eager to obtain or do; zealous with sincerity...", and I think only part of that definition is met by the Mountain Goats' songs. They're really more honest than they are earnest, as the speakers don't really have an objective but to tell the story.