Update October 2014. I developed the envisioned CSL validator frontend myself. It is live at http://validator.citationstyles.org/.
Update August 2011. This highlighting file has now been merged into Kate: https://cgit.kde.org/kate.git/commit/?id=377b90dd5d827764e70a91eeff0897831e1f6897
Today brought quite some satisfaction: I finished writing my second research paper. But the focus of this post is on another, related, milestone: this paper ...