@eschwartz: I wrote "unnecessary". As in some people could objectively claim that such functionality is farther out of scope of lets say "original role(s)" (library organisation, metadata clean-up, format conversions) Calibre then supporting some "format no one uses anyway" (= dual mobi).
I myself use Calibre's Editor and am glad it exists (was especially happy when Calibre got ToC editor & "embed metadata" button), even if I still prefer Sigil for some thing like IMHO better UI for setting semantics and quicker way of jumping to CSS class via "Go to link or style".
If any other functionality I don't use was broken and I was somehow made aware of that fact I would again inform "the right people" that it needs fixing. I'm a busybody
