I'm frankly baffled. According to debug print statements (in read_font_record and write_font_record) when converting via the command-line, calibre is always
obfuscating the fonts -- stand-alone KF8 or
I need to revisit Mobi_Unpack's handling of obfuscated fonts, because it unpacks the joint file's fonts as unobfuscated and the standalone file's fonts as obfuscated (although I know the same font handling routine handles joint vs stand-alone KF8s).
I think I'll just change calibre's write_font_record to:
def write_font_record(data, obfuscate=False, compress=True):
for now. Always unobfuscated in KF8.
I know Kindlegen/KindePreviewer doesn't produce xor'd, obfuscated fonts (I think Amazon only obfuscates them before/upon delivery).