Today at #InkscapeHackfest one of our most long-standing bugs was fixed and we can now have a top-left origin in documents! Thanks Thomas!
Bug #170049 (sf859982) “Inverted ruler co-ordinate system” : Bugs : Inkscape
The y-axis of the rulers' co-ordinate system is inverted (increasing upwards), and places the origin on the bottom left of the viewport. The SVG spec places the default origin on the top left of the viewport, and has the co-ordinate system increasing to the right and downwards.