Kaomoji

The difference from :-) is orientation. Western emoticons are read sideways because they were built from a keyboard with about ninety usable characters, so the mouth had to be a bracket turned on its side. Kaomoji are read upright, and they can be because Japanese input methods have always had a far larger character set to draw on — the eyes carry the expression rather than the mouth, which is also why they read as more expressive with fewer strokes.

That larger character set is where the practical problem comes from. A kaomoji is assembled from Japanese punctuation, Korean jamo, mathematical symbols, Cyrillic and box-drawing characters all at once — the shrug alone uses a macron, a katakana tsu and two backslashes. If a font on the receiving end lacks any one of them, that part becomes a replacement box and the face falls apart. There is nothing wrong with the text when this happens; it is a font coverage problem, and it is why some faces survive being pasted into a game chat and others do not.

One genuine gotcha with the shrug: ¯\_(ツ)_/¯ contains a backslash, and anywhere that treats backslash as an escape character — a shell, a JSON string, some chat clients with markdown — will eat it and leave you with a one-armed shrug. In those places the backslash has to be doubled.