Does the author go as deep as we do?

After reading The Altar, and discussing/analyzing it in class, as we look into each and every literary technique for an underlying meaning, it makes me wonder how far the author went into setting up this poem and if all of those meanings were implied or if they were just a product of the overall meaning he was trying to get across.

For example, the shape of the poem is an obvious blatant attempt to apply extra meaning to the words, but like we discussed in class, his use of the word "O" in the second to last line... was that an attempt to inflect a more personal feel to that line, to make the altar a part of himself or was it just a way to make the poem flow, and work better.

As someone who has never sat down and written poetry I would be interested to here from you guys how much work goes into each little thing like that beyond the basic structure and format.