The functionality was always there (think ê vs ê), so properly handling glyph segmenting a string requires returning a `Vec<Vec<char>>`, which makes these emoji actually very useful: it makes it more likely that implementations will do the right thing by giving people from "predominantly ASCII" locales a "tool" to exercise those codepaths. Widespread emoji adoption is likely the best thing that could have happened to proper text handling for users outside of the anglosphere.
Combining characters are trivial to deal with. Some of the new emoji compounding uses things like the color squares to alter an emoji and you are forced to have a table of which emoji are dual function to know if they merge with their neighbors or stand by themselves.
Nothing else in Unicode acts like that. You can't properly parse complex emoji glyphs from a random starting point because you need previous context to know how to interpret following codepoints. With combining characters you just skip ahead to the next non-combiner.
