```On Fri, Sep 17, 2010 at 09:36:09PM +0200, Frank Mittelbach wrote:

> Hi Heiko,
>
>  > LaTeX2e uses \zap@space to remove the spaces in the option lists.
>  > As a side effect \zap@space also removes the braces around the
>  > comma, because the group is followed immediately after a space:
>
> since you already looked at the different implementations, any suggestion on
> how to best improve the LaTeX2e behaviour?

Because of the frozen nature of LaTeX2e I don't expect that LaTeX2e
it that way.

Example, preserving spaces in option names (with or without around
equals) will break, for instance:
\documentclass[a4 paper, 12 pt]{documentclass}

My recommendation for package authors that use key value interfaces
is to provide a \<package>setup command for setting the options
and getting rid of the option limitations of LaTeX2e.

Also setting options in \usepackage makes problems with option