Oh, it's a long lasting thing. Ever since the Kairi and Namine essay, along with me not shutting up.
I guess it's so "in" nowadays to hate on Xion that people forgot they used to call me names for acting that way about Kairi. Do ho ho.
And btw, your post is interesting--Kairi being corrupted by the light. I think she already has been at this point in the series, hence her sudden and quick-to-judge attitude of Riku at the beginning of KH1. "You know, Riku's changed," and "let's take the raft and go-just the two of us!" Hell, I'd take it if it meant she was given an actual role. c: