1. You're right about the typo. I misspelled Arial. And agreed about the problem with it being not free to distribute. That was an oversight on my part.
2. The default font in my Xiphos setup (under Windows with English as the locale) does not support Devanagari at all.
3. Xiphos sets fonts either per module or per language.
4. I've had some acquaintance with the Devanagari script for over 40 years, even though I'm not fluent in the Hindi language. I may be very rusty with its orthography through non-use, but I can tell when there is a rendering issue. And there is in Xiphos when Linux Libertine or Tahoma was used. Problem suspected in webkit.
5. Therefore there is still an issue - though whether it's restricted to just some front-ends is a harder question. The module displays OK in BD and And Bible.
6. Maybe the compromise is to suggest a suitable font in the About, rather than specify a font as a property?
I'd value further consideration.