Joseph Wright writes:

 > As I said in my other mail, at the moment xparse is about LaTeX2e
 > conventions using LaTeX3 ideas. So there is no danger of dropping
 > trailing optional arguments at the moment! I'd also note that there is
 > an outstanding question on the coffin code about whether optional
 > arguments, a keyval approach or something in between is best.

yeah there is :-) I'm dead against it .. no not really. But I'm not really in
favor of it either. But not here under this subject line

 > So I certainly don't regard this question as resolved one way or the other
 > at present: at the moment, I'm just worried about spaces :-)

very wise. :-))