It was brought to my attention that the Droid Serif fonts in the distribution package from BlogKindle were invalid/broken. Kindle reader software replaced the broken fonts with the default font, which was SansSerif-Regular. To fix this issue, I replaced the bad Serif fonts with valid
Android Droid fonts, but I could not find complete Unicode set, so I used the ones with Unicode sets up to Cyrillics (which is more or less all I needed anyway). You can
download the package again. I tested it with Russian Mobi texts, works fine.
I converted the Liberation fonts package into KDX as well, so
it can be downloaded and tested. I believe all the Liberation fonts are valid, and they may have more Unicode sets, though they don't seem to have Chinese and Japanese characters either.
For those who need Far Eastern characters I would recommend finding a decent complete set of Serif fonts (Regular, Italic, Bold and BoldItalic) and rebuilding the Droid package with those fonts.