Gave it some more thought, and here's a follow up.
I have a bilingual (English and Urdu) blog, and while I would want to
override the smart quote substitutions for my Urdu posts, I would like
to use the default ones when writing in English. Same is the case for
other Markdown extensions (such as Footnotes, which lets you set the
backlink text and backlink title, and which I would only like to
override for Urdu posts).
So, could it be possible to configure the settings for Markdown
extensions on a per language basis?
-- Saadat