[kijin]

In defense of the Korean airport staff, they might have been more accommodating if the "ö" was completely and obviously broken, like "£‡�". Spelling it as "oe" makes it look like there are no encoding issues, in which case strict checking makes more sense.

It's much easier to identify mojibake (they tend to be extremely obvious in CJK encodings) than to remember canonical spellings and other variations in a whole bunch of different languages. Airport staff probably know that "oe" and "œ" are interchangeable, but that's about it.