Hangul is phonetic, but with letters arranged into syllabic symbols. In Spanish there's a gibberish construction where you reverse syllables ("al vesre", meaning, "al revés", which means "backwards"). Reversing text makes little sense except as an interview trick question, I guess, but if you must make sense of it, then reversing syllables makes more sense than going further.
BTW, you can reverse Unicode (in any UTF), so long as you don't really care about the semantics of the result -- if all you want to do is reverse the codepoints, you could. After all, it is an interesting programming interview trick question, though admittedly then "you can't really" answer is more fun because you get to talk about glyphs and ligatures and so on, and natural language, thus demonstrating your mastery to the person who was trying to trick you.
BTW, you can reverse Unicode (in any UTF), so long as you don't really care about the semantics of the result -- if all you want to do is reverse the codepoints, you could. After all, it is an interesting programming interview trick question, though admittedly then "you can't really" answer is more fun because you get to talk about glyphs and ligatures and so on, and natural language, thus demonstrating your mastery to the person who was trying to trick you.