wrong, I know that most of them can be tweaked via the pref file, but 
    they should be resolved out of the box.

A disagreement between Emacs conventions and GNOME conventions is not,
ipso facto, a problem in Emacs.  We might want to change some of these
things in Emacs, but not necessarily.  In some cases it might be better
to change GNOME.

Emacs has its own customization mechanisms, and in many cases we have
chosen the defaults we think are best.  We might decide to change some
of them but there is no reason to change them all.

    - vertical scrollbar should be on the right (for LTR, at least).

Scroll bars on the left are better, so we won't change that default.

    - background and foreground colors for the default font should be white 
    and black.
    - background and foreground colors of text selection should obey the 
    system default (in moz, we have the background color right but not the 
    foreground, we'll fix that).

We've made careful choices of default colors in Emacs, but we can
consider whether there is an equally good choice that accords with
those conventions.

    - the text cursor should be like a |, not an filled rectangle. Its 
    default color should be black and not pink.

The box cursor will remain the default.

    - on the content area, even outside of the text, the mouse cursor should 
    not be an arrow but a |--| rotated 90° and by no way pink but black.

I have no particular opinion about this.

    - tooltips haven't the system background and foreground colors and 
    should appear below the mouse pointer.

I would not mind if we changed the defaults for the tooltips.