@grunk:
But there are metric buttloads of symbolism all over the place. Oda loves putting symbolism in his manga.. it's everywhere..
grunk, I think the key thing you're missing is the difference between an "allusion" and a "symbol" –
An "allusion" is a casual reference to something within another thing -- that may or may not go any deeper than that. So for example, when you write the phrase "D'oh!" in a thread reply, you're alluding to Homer Simpson, but that doesn't necessarily mean that you're trying to draw some profound parallel between Homer and whatever else it is that you were talking about.
Let's take the term Asura. It's found in three religions:
Buddhism, Hinduism and Zoroastrianism (<–nudge nudge). In two of them, the Asura are minor and materialistic deities. In the third, it's a different class of deities. Now, maybe Oda is trying to say something obscure about the need to cut oneself free from materialism in order to transcend worldly desires, blahblahblah ..., but more likely -- since he's admitted to doing this before in other contexts -- he just chose the name because it "sounded cool" and because the third religion also has Zoro's name in it. So it's not a critique of materialism, it's a silly pun. Make sense?
In contrast, a "symbol" is something that usually has a deeper significance than an allusion, and it often requires a lot of "unpacking" to explain. Luffy's straw-hat is a perfect example of a symbol in One Piece. You could say" "it's just a hat, dinty!" -- but think about what that hat signifies to Luffy, to Shanks, and to the Straw Hats (who are named for that hat, goshdarnit).
It's Luffy's treasure, his flag, his promise to Shanks, his promise to his crew, etc. And that's why it made such a fitting object to bookend the time-skip chapters. That's the power of an effective symbol.