My Linux is Lubuntu 16.0.4.1 LTS installed Japanese and English language.
And I installed default inkscape binary(0.91 r13725) using "apt install inkscape".
libcairo2 is version 1.14.6.
The snapindicator does not have the problem. It displays translated japanese exactly.
It seems to me that your environment have some problem.
On Linux.
My Linux is Lubuntu 16.0.4.1 LTS installed Japanese and English language.
And I installed default inkscape binary(0.91 r13725) using "apt install inkscape".
libcairo2 is version 1.14.6.
The snapindicator does not have the problem. It displays translated japanese exactly.
It seems to me that your environment have some problem.