Artlessly (edit 1.)

[Acappella]

against silky, sun-slashed hair
"Do you know?" was murmured. voice skin-deep, The passive voice here bothers me a bit.
diaphanous; get a grip and stay
still. his bones scratch like lottery tickets, 
burn exactly the same                  This image has so many layers. These two lines are a roller coaster in a good way. "Bones scratch " is a jarring pair of words but                                                       the "lottery tickets" gave a lighthearted, hopeful feel until the burning image came in. It creates an enticing mystery around the                                                    character.

"南京is a city where people go to laugh."  
no, 
she hadn't known. he laughed like someone
who couldn't stand the world- not all the way-
not the parts that needed to be- so he hoarded
the bits of himself
that really mattered

his language came to life even as his lips
wilted against the side of her head. 
"纽约市, love," 
his words inflamed by strong sunlight,
"people go to die there. Whether they know it
or not." they both looked out to the world, 
knowing different things

he talked his home to death. cut through its smoke 
and its gruel with disposable razors, grief seen but not heard, This is where the poem really hooked me and I wanted to reread to understand the male character                                                                                                           better. It's an excellent description of a person missing and grieving for a place.
flowers thrown curbside, flushed dark with damp. 
somehow, he never drank. a habit that skipped
generations, it was concluded. the stars fell upon her 

they were both dark-haired, dark-eyed, the careless sort of dark, brusque,
obsessive, the lines around their characters inked with clarity,                    I can't really wrap my head around people who are careless, brusque and obsessive.                                                                                                                Someone might be careless about some things and obsessive about other things, but as general                                                                                                                  descriptors those qualities oppose one another. 
precision, stunning; they were both best when apart, focused upon 
their art, the brush themselves, the picture their personalities I think the last line is the weakest of the whole poem.  It just... lays too much out there. The poem would end better on the word "apart". 

This is my first critique. I hope I have done your poem some justice because I think it is very well done. The thing I am questioning about the poem overall is the character focus. The whole poem seems to be about the male character. He is very interesting with his personality and situation laid out in vivid detail. We know very little about the female character except that "the stars fell upon her" -this phrase is ambiguous to me. That would be fine, except that the last stanza switches the subject to the two of them as a couple, or un-couple as it were. I think you should either add some detail to her character earlier in the poem or really rework the last stanza with the focus still on the male character.