I've looked back through the thread and can't find a post which covers exactly why I added this check. It has the effect of giving you a set of books that have calibre covers in them, which by association means that if you export them using calibre (or use Modify ePub "Update metadata") that their covers are replaceable.
However this is only a *subset* of books that "could" have their covers replaced when exporting/updating metadata. An epub doesn't always have to have been converted by calibre previously for this to work.
I think it would be much more useful to have a check which can tell you which ebooks need calibre conversions or not to replace the cover (well, until my new Modify ePub cover insertion feature appears of course).
So I would like to add a "Check replaceable cover" option in Quality check (along with a "Check not replaceable cover" option), and kill off the existing two inline cover checks.
Any objections? If you happen to use the feature as it exists currently I'd love to hear from you. Otherwise I'm going to assume the answer is good idea
