It seems to me that thee definitions on ISO-8859-* are ambiguous
in RFC1521 and draft-ietf-822ext-mime-imb-00. Perhaps, ISO-8859-*
is intended to be used with 8 bit without designating escape sequences.
But there is no such description.
Treatment of bi-directional text is also ambiguous. The following
statement
The default handling of bi-directional text is in visual
mode [RFC1556].
should be added. Note that the bi-direcitonality issue is not
8859 specific. There can be bi-directional US-ASCII text.
Masataka Ohta