These strings can't be added to Transifex because of how the banners are configured.
The moderator agreement itself is only available in English for legal reasons, so between that and the fact that they're up for a limited time, we decided not to translate the banners in this case.
Something's wrong with whatever parses the search string, when you add the is:a bit. Note the response:
We couldn't find anything for दव सपरण
It has actually split out the combined characters into separate ones.
If I search for "द्वा सुपर्णा" is:a, it works correctly.