On a quasi-related note, is there some construct to translate little blurbs of text for the reader? If these were full-fledged untranslated paragraphs of French, I'd run it through Google Translate and stick the result in a footnote. But, for these little Poirot exclamations, most of them are trivial and only some use words I don't recognize.
I was thinking of commandeering <abbr title="...translation...">french phrase</abbr>, but though it works in Calibre, it doesn't as a kepub on my Forma. A pure <aside>...translation...</aside> just breaks the paragraph and dumps it right there. <ruby>french phrase<rt>the translation</rt></ruby> looked interesting, but it puts the individual translated words over their corresponding untranslated words (instead of just putting the whole translation over the untranslated phrase).
Right now, the best I can come up with is a full-fledged footnote to properly set the translation off from the paragraph.