@pwr - as I have posted previously I don't have a Fire so those check and fix options related to MOBI have been made "blind" based on other people's suggestions, and the question of other formats like AZW and AZW3 hadn't come up yet. I don't use those formats personally so I know nothing about them.
What QC options would such a change apply to - does that mean all of those "Check Mobi" menu options as well as the "Fix MOBI ASIN" one? And how sure are you about the EXTH headers being the same - can anyone else confirm it?
I am also wondering if as per this post
by Kovid I should add another Fix option to allow *removing* the ASIN/resetting the cdetype? Because it sounds like for *some* books due to bugs in the Kindle Fire then running the Fix MOBI ASIN option is going to give you a book that will crash? And that in such a case Kovid is recommending a conversion to effectively reverse those EXTH values? I really haven't bothered paying attention to any of this, the 4G Kindles were of no interest to me personally so if anyone has an opinion feel free to share it, I am not motivated to go hunting through loads of threads myself about it. Perhaps it may just be a short term thing and Amazon pull finger with a firmware release to fix it making it not worth worrying about.
As for the UUID - to be brutally honest I had forgotten that a calibre book even had one
. That is certainly an easy change to make.