Hi Pilou,

> If there any problem just ask to developpers to make something
> for that! maybe there

Well, it seems that some of this behavior has already been reported as a bug.

For example here is a recent bug report that someone submitted about normals changing just when entering/exiting edit mode without doing anything else:
http://projects.blender.org/tracker/?group_id=9&atid=498&func=detail&aid=26405

Unfortunately the Blender dev says that they don't intend to fix it anytime soon and the bug report was rejected and closed.

- Michael