Twitter is not a "basic case", it's a case where the length limit is arbitrary and the specifics don't matter much anymore. Usually when you want to segment text that is not the case.
Edit: basically, my problem with your original comment is that it helps spread the misinformation that a lot of these things are "just" emoji problems, so some folks tend to ignore them since they don't care about emoji that much, and real human languages suffer.
This, to me, is an argument for emoji being a good thing for string-handling code. The fact that they're common means that software creators are much more likely to notice when they've written bad string-handling code.
Whatever platform you're using should have an API call for counting grapheme clusters. It may be more complex behind the scenes, but as an ordinary programmer it should be no more difficult to do it correctly than it is to do it wrong.
Another contributor to this is that programmers love to hate Unicode. It has its flaws, but in general folks attribute any trouble they have to "oh that's just unicode being broken" even though these are often fundamental issues with international text. This leads to folks ignoring things because it's "unicode's fault", even though it's not.