Obsolete writing-mode values, glyph-orientation properties

Dear SVGWG,
  I've updated the Writing Modes spec to address

1. Clarifying the obsoletion of the old writing-mode values,
    and how they can be mapped into current CSS:

   https://drafts.csswg.org/css-writing-modes/#svg-writing-mode

2. Added a section defining the glyph-orientation-vertical property
    and its mapping to text-orientation:

   https://drafts.csswg.org/css-writing-modes/#glyph-orientation

I would greatly appreciate your review on whether these sections

   a) are technically clear and understandable
   b) express what the SVGWG wants to say about these features

If not, please let me know how to improve them so we're all happy. :)

I would also appreciate if someone in the SVGWG could figure out
what the "inline progression direction" actually does in SVG
documents, since last time I tested them, implementations didn't
really agree on their interpretation of the 1.1 spec...

Thanks!
~fantasai