> Actually, U+10FFFD is the maximum legal codepoint, the last two codepoints on every plane are reserved and declared as noncharacters. Few parsers are really s

> Actually, U+10FFFD is the maximum legal codepoint, the last two codepoints on every plane are reserved and declared as noncharacters. Few parsers are really so strict. This is what Unicode 11.0, §2.4 says: Noncharacter code points are reserved for internal use, such as for sentinel values. They have well-formed representations in Unicode encoding forms and survive conversions between encoding forms. This allows sentinel values to be preserved internally across Unicode encoding forms, even though they are not designed to be used in open interchange. It would wrong for a general-purpose parser to reject these codepoints.