However, using any format without strict adherence to the standard makes no sense.
That, as browser builders found to their chagrin, is rather difficult to accomplish. Generally speaking, when a "format" has had time to develop in several directions before a strict standard came about or when it is used for things it never was thought to deal with, one should follow the old IETF principle:
be strict with what you emit but liberal with what you accept.
In this case, as with any text-based format, one must be ready to accept as many definitions of "text" as one possibly can, which is not as easy as it sounds. A few forms of text (UCS2, UTF16, ...) can be inferred from a "mark" in the text (the BOM), but with others one has to resort to "wild guesstimation", to byte-frequency analysis or ask the user what the heck he meant. Telling the user: "I don't like that file! Correct it and try again!" should be an absolutely last option reserved only for extremely bad-formed text.
IMHO, of course