The emoji "" can't be normalized further -- it's a "" followed by a "". If you just split on code points rather than grapheme clusters, even after normalizing, your naïve truncation algorithm will have accidentally changed the skin colors of emoji. Or turned the flag of Norway into an "". Or turned the rainbow flag into a white flag .
EDIT: oh lord Hacker News strips emoji. You get the idea even though HN ruined the illustrations. Not my fault HN is broken.