@cscat: Thanks for the clarification
* The 'Before You Go' screen is shown for every book with exth 113 (ASIN) set. Calibre does it by default, unless you check the 'Enable sharing on facebook' mobi setting.
* If we forget the KF8 renderer issues, we're left with the fact that a custom freetype *does* leads to LTR broken persian script (broken ligatures) in the mobi renderer. That's weird, because that shouldn't be FT's job at all, and I can't think of a reason why it would happen off the top of my head, but since Amazon probably patches FT like crazy, and they're using it under the FT license, we don't have the sources to check... And since it doesn't really help to have it ligatured but LTR, I don't think it's worth investigating, if it doesn't hurt other LTR scripts... ^^
Just for my piece of mind, would you mind linking me to a plaintext (or html) block of persian script?
EDIT: ... Or I could just unpack the samples you posted earlier. >_<". I think I need another scotch, the last one wasn't effective enough.