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Until about the 2010s, many computer systems rarely, if ever, needed to process characters beyond the BMP, and as a result, some software may might still (at the time of this writing: 2015even now, in 2021) simply assume that no characters beyond the BMP are valid, and strip such characters or otherwise corrupt them. We have often seen SMP and SIP characters input and stored correctly in a CMS, only to have pairs of U+FFFD (REPLACEMENT CHARACTER) returned.

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