Some platforms (e.g., Android) have methods specifically for asking how to edit a string following a backspace. However, there's no standard Unicode algorithm t

Some platforms (e.g., Android) have methods specifically for asking how to edit a string following a backspace. However, there's no standard Unicode algorithm to answer the question (and I strongly suspect that it's something that's actually locale-dependent to a degree). On further reflection, probably the best starting point for string editing on backspace is to operate on codepoints, not grapheme clusters. For most written languages, the various elements that make up a character are likely to be separate codepoints. In Latin text, diacritics are generally precomposed (I mean, you can have a + diacritic as opposed to precomposed ä in theory, but the IME system is going to spit out ä anyways, even if dead keys are used). But if you have Indic characters or Hangul, the grapheme cluster algorithm is going to erroneously combine multiple characters into a single unit. The issue is that the biggest false positive for a codepoint-based algorithm is emoji, and if you're a monolingual speaker whose only exposure to complex written scripts is Unicode emoji, you're going to incorrectly generalize it for all written languages.