User blog comment:ChishioKunrin/Taiyang got a tattoo/@comment-26397825-20151027114325/@comment-24198837-20151028194550

I like the idea that you simply choose your own symbol - some choose the symbol of a parent or relative - Ruby to remember Summer, Weiss because she has to "uphold the Schnee name", or something like that.

Yang, by this logic, likely chose to make hers a fusion between Summer and Taiyang's - assuming this happened before she was told about Raven. Maybe Yang's symbol is in-part inspired by Raven. Maybe Raven just doesn't have a symbol.