I18N rebuttal - for review

I have updated my draft rationale/rebuttal (attached)

The main difference is the new final section specifically discussing the 
points raised in the formal objection. I have also added section headings 
etc, and made some changes to address comments from DaveB.

I am increasingly unclear what role it will finally play.

Possibly for 2nd LC it is best to change the intro a bit and attach it to the 
issues list, and maybe link to it from the call for review (near the link to 
the I18N objection).

The issue of what role it plays in a call for advance to PR is less pressing.

Jeremy