are you sure that deleting the whole grapheme is actually what the Tamil or Korean user wants?
I'm not, but I think it's the only sane thing for a text editor to do if you don't want it to incorporate a ton of language-specific rules. The UAX actually does make a distinction between "legacy" and "extended" grapheme clusters---if you're handing "delete", you'll want to use "legacy clusters" to separate the two Tamil marks; but for text selection, use "extended clusters" will combine them (it's a little bit more complicated than that, but there are properties of Unicode that allow you to handle the "preferred" method for editing a script, while remaining mostly language-agnostic).
Hangul is trickier, but input happens through an IME that "composes" the characters before they are committed to the editor.
The IME will perform component-wise deletion, but once it's committed, the editor will operate on the grapheme. It's not a perfect solution, but keeping the composition/decomposition rules for the language in the IME seems preferable.
I'm not, but I think it's the only sane thing for a text editor to do if you don't want it to incorporate a ton of language-specific rules. The UAX actually does make a distinction between "legacy" and "extended" grapheme clusters---if you're handing "delete", you'll want to use "legacy clusters" to separate the two Tamil marks; but for text selection, use "extended clusters" will combine them (it's a little bit more complicated than that, but there are properties of Unicode that allow you to handle the "preferred" method for editing a script, while remaining mostly language-agnostic).
Hangul is trickier, but input happens through an IME that "composes" the characters before they are committed to the editor. The IME will perform component-wise deletion, but once it's committed, the editor will operate on the grapheme. It's not a perfect solution, but keeping the composition/decomposition rules for the language in the IME seems preferable.