Hi all,
I think in the same way as Dmitry.
It might be obsolete but, as far as I searched, under the setup
\definefontfeature [texligatures] [tlig=yes]
\feature[+][texligatures]
{''} produces right quotation correctly but left quotation seems
not correct (I don't know why).

It is true quotes are language dependent but sometime we need
language independent quotes. So it will be  nice if we can use
{``}, {''} and \quotation at the same time.

Best regards,
Atsuhito Kohda