The size doesn't actually make much difference, but they're different Unicode characters and you can't type the wrong one by accident.
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Basically it means whoever typed it was copying and pasting or trying to look up a charmap or something silly, not actually typing Japanese.
You don't actually have to be able to tell them apart visually because which one is intended is obvious by context. Like I and l in English.
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If you saw someone write "EngIish" you'd know they don't know English and didn't type that but rather copied and pasted letters or used OCR.
Thanks. Twitter will use this to make your timeline better. UndoUndo
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