> My understanding is Unicode (and therefore UTF-8) can encode all the codepoints encodable by Shift JIS
Trivia: There are some variants of ShiftJIS where this isn't entirely true. The traditional yuugen gaisha symbol, for example, which is analogous to U+32CF (LTD), is not supported. The /VENDORS/APPLE/JAPANESE.TXT file uses a PUA designator and then a sequence of four Unicode code points to convert it.
Trivia: There are some variants of ShiftJIS where this isn't entirely true. The traditional yuugen gaisha symbol, for example, which is analogous to U+32CF (LTD), is not supported. The /VENDORS/APPLE/JAPANESE.TXT file uses a PUA designator and then a sequence of four Unicode code points to convert it.