Code:

$ = SetOption("NoMacrosInStrings","Off")
? @KXI
? CStr(@ERROR)+": "+@SERROR
? '@KXI'
? CStr(@ERROR)+": "+@SERROR

I would expect the same messages and errors. The message "<unknown:KXI" is IMHO unexpected. Throwing an error would be nice. But as NoMacrosInStrings is Off, the error should be the same, just as the return value should be the same.