RE: Missing Exception in MediaList interface

:So, I guess the comma should be definitively excluded from the 
:syntax of a medium: SYNTAX_ERR If the medium contains a 
:comma character.

Yes. From  CSS2:

medium : IDENT S* ;
IDENT : nmStart nmChar ;
nmStart: [a-zA-Z] {nonacsii} {esc} ;
nmChar: [a-zA-z0-9] {nonacsii} {esc};
nonacsii: {^\0-\177}

The literal [,] is not a legal part of an IDENT term, nor can whitespace
appear within a medium term. Thus, media.appendMedium("print, braille") or
media.appendMedium("print braille") should throw SYNTAX_ERR, as Phillipe
says. Though strictly speaking media.appendMedium("print     ") is a legal
medium term. But this just requires a comment on whether the method will
barf in that case.

-Bill