Li Yu's poems are very plain in language. They were written like 1000 years ago, but an elementary school student shouldn't have too much difficulty in understanding them. But maybe that's because the poems are so popular, they are a part of common language now. Li Yu's style was very different with the popular Hua Jian style(花间派) of his time, which was very indirect, elusive, highly decorative etc. I think poems are all originally direct and clear, like those poems in the Classic of Poems(诗经) "窈窕淑女,君子好逑", but to avoid cliche and banality, poets had to seek indirect ways to express themselves. In stead of talking about love, longing, friends etc, they talked about flowers, water, moon, spring etc. etc. I believe a classic example would be Spring River Flower Moon Night(春江花月夜). Then again, as time went on, the indirect ways became cliche too. Like someone( I forgot his name) said, the first person who compared women to flowers was genius, the second was an idiot. The Hua Jian Style was extremely indirect in style, in stead of referring to the moon directly, the poets often said something like, jade tile(玉瓦）, laurel flower（桂华） etc. (An exemplary poet would be Wen Tingjun(温庭筠) )
Li Yu had a very special personality in his poems. It's probably as much from his enthusiasm in Buddhism as from his experience. One moment, he's endearing and personal, another moment he became aloof and philosophical. He wrote in plain language, and very cliched analogies like running water, falling flowers, yet there were undeniable beauties in his lines. You don't have to know his stories. It's such an easy pleasure just to read those famous lines, yet after a second, the immenseness of his sadness began to sink in and hit you like ten tons of bricks.
I opted for the sadness of the poem, which I believe is what it's really about, but at the expense of the beauty of the style. As for the small swings of the mood, it's really way beyond my ability. Translating classic poems is really a daunting task, but a lot of fun too! Cheers