...that may well be related to the source files, but it's so unpredictable that I'm hesitant to assume anything. This appears in some KFX books (and, as far as I've been able to determine, only KFX books) converted to epub.
Sometimes word/phrase formatting — such as a word appearing in italics, "<i>Ibid.</i>" — is hardcoded:
and sometimes the conversion results in a style that is the format variation only, included in both the stylesheet and appearing in the text as:
Code:
<span style="class_s47">Ibid.</span>
This can result in some bizarre display glitches, but I'm more puzzled that they're unpredictable. The difference can appear in volume 2, but not volumes 1 or 3, of the same series from the same publisher released as e-books in the same month. I've seen this across multiple publishers. The only predictability is that they're consistent across the KFX (that is, it would be every appearance of italics in a given KFX source — or none of them).
Please confirm whether this is something internal to KFX's conversion routines, something that's slightly broader in Calibre's conversion routines, or something that's in the source files (such as different people doing the conversions at the publishers doing something different in InDesign or Word resulting in slightly different output code — which can/does happen). If you can, that is... and this is far from urgent. Just bizarre.