"Moonlight" was apparently Clark Ashton Smith's (CAS) very first poem to be published, in a 1910 issue of the Overland Monthly, a digital copy of which can be viewed at Hathitrust:
(The poem by "C. Ashton Smith" is at the bottom of that page).
Right away, I notice that this poem has an odd number of lines, which is a first among the early poems by CAS that I have read so far. That suggests to me that CAS is doing something interesting with the poem's structure.
After having read it several times, it seems to me that there are three distinct sections in this poem, as shown below. My arrangement violates the rhyming pattern, but nonetheless I believe I'm on the right track.
Section 1 has a a nice abba rhyme scheme, and a paints a pleasant picture of the moon rising amongst the stars. Everything is delivered in a single sentence with simple line turnings at either a comma or period, so that the reader is encouraged to pause at the end of the line.
But Section 2 is something different. There are two sentences here, but the author has used line turnings quite differently, and has interrupted the smooth rhythm we encountered in Section 1. The first sentence ends at the beginning of line 7 ("And subtle glamour."), while the second sentence quickly encounters an odd line turning immediately followed by a pause on line 8 ("It seems--"). In encountering these pauses in unexpected places, the reader likely waits just a bit longer before moving on.
Moreover, the pleasant image from Section 1 is suddenly disrupted with some words and phrases that suggest all is not quite as placidly earthbound as it seems: "mystery", "realms unknown", "worlds that lie beyond our ken", "glimpsed in dreams alone". Coupled with the longer pauses I describe in the previous paragraph, I think that CAS really wants the reader to linger on these otherworldly images, and he's architected his lines to encourage us to do just that.
Section 3 initially continues in that same vein by using the word "witchery", but importantly the complete phrase is "tender witchery". Following phrases seem to return us to the gentle sensations of Section 1: "softly doth erase", "a pallid beauty", "a white, enchanted pall." Section 3 also returns us to the simpler rhythm of Section 1, with almost all lines ending with either a comma or period, so that the reader is once again encouraged to pause at the end of the line.
Color me impressed. CAS is using the poem's structure and his word choices very carefully to heighten the interest in the middle of the poem (Section 2), and to present the reader with a slightly off-kilter experience in that section, before returning us (in Section 3) to the gentler territory in which he began the poem (Section 1).
Although this poem saw magazine publication, I'm surprised that CAS never included it in any of the book collections published in his lifetime. Of his early poems that I've read so far, this one strikes me as having the greatest evidence of the artist's skills, but used in a way that is not flashy or overwrought.