Why does 「歐陽」 sometimes get split on a passport?

Question

Weirdo · Accepted Answer

A passport splits a name into a primary identifier (surname) and a secondary identifier (given names). Taiwan’s foreign ministry lets the compound surname 「歐陽」 be romanized as one word or two; a space or hyphen between those words becomes a single filler < in the machine-readable zone, and a foreign system may treat the second half as a given name.

Taiwan’s Bureau of Consular Affairs is explicit: Latin-letter names go surname first, given names second, with a comma after the surname. A compound surname may be transliterated as one word or two, with a space or a hyphen in between. Their example is 范姜大明, whose surname may be written as one block, two words, or a hyphenated pair. If 「歐陽」 is filed as two words, the visual zone still looks like one family name; machines and a foreign immigration desk see two components.

ICAO Doc 9303 Part 3 splits the holder’s name into a primary identifier (usually the family name) and a secondary identifier (given names). In the machine-readable zone the primary identifier is followed by two fillers <<, then the secondary identifier. If the primary identifier has more than one component, each is separated by a single < — hyphens are split the same way. Two-word or hyphenated 「歐陽」 therefore becomes something like OU<YANG<<given-names. Software that only cuts on the first < can read the second character of 「歐陽」 as a given name. Filing it as one word, with no space, is the form that is harder to split.

Why does 「歐陽」 sometimes get split on a passport?

A compound surname can be filed as one word or two

The machine-readable zone turns spaces and hyphens into <