Text reverser

Three different reversals: the characters, the order of the words, or the order of the lines. They are genuinely different operations and people usually want one specific one.

Reversing characters is where an implementation detail becomes visible. Doing it naively splits a string into UTF-16 code units, which breaks any character outside the basic range — emoji, many CJK characters and flag sequences all come apart into meaningless fragments. This iterates by code point instead, so those survive. Combining marks are the remaining edge: an accent stored separately from its letter ends up attached to the wrong letter after a reversal, which is a real limitation of reversing text at all rather than a fixable bug.