I had cut and pasted a section of a doc from another person in my pages document and now that section is flagging my english words as misspelled and when I check the spell checker it tries to change it to the french word.
Think of it this way —
The universal standard character superset is unified. The many small character sets of the nineteen-seventies, nineteen-eighties and nineteen-nineties isolated computing communities because these small character sets had incompatible constitutencies. Unification of these small sets into a superset allowed the input-creating software and the output-consuming software to share the selfsame character superset which is what makes computerised communication possible.
However, because the character information is unified, there is no information in the standard character superset on the specification of character semantics. ISO10646 / Unicode does not encode orthography, so it is necessary to tag universal character information with unique ISO 639 language identifiers to specify character semantics. The author is best positioned to disambiguate which writing system in which world script is being input.
ISO 15445 HTML published in 2000, ISO 19005 PDF/A published in 2005, and ECMA 388 OXPS published in 2009 ask that the author specify character semantics by tagging with unique ISO 639 language identifiers. The standards and their guidelines also ask that the author disambiguate acronyms and abbreviations. Impact writing on paper is different from image writing in digital documents: the author has much more work to do in order to be understood by the audience.
/hh
