obs-text character encoding and error handling; duplicate parameter names in Content-Type

obs-text character encoding and error handling; duplicate parameter names in Content-Type

I have two issues.

1. obs-text character encoding and error handling

What is the character encoding used when a header field value contains obs-text, and particularly
parameter values in Content-Type?  Is it ISO-8859-1, UTF-8, or something else?  Or is the encoding
  undefined?  Error handling rules for obs-text, unlike for obs-fold, are also absent.

2. Duplicate parameter names in Content-Type

Suppose that the following Content-Type is received:

    text/html; charset=iso-8859-1; charset=utf-8
 
What is the resulting value of the charset parameter?  Is it iso-8859-1, utf-8, an error, or undefined?
(This issue also applies to Content-Disposition, Accept, and other header fields that use parameters.)
 
--Peter