I use Book Antiqua for my main text. Some parts are in italics. When I sync with external folder (or at least I think that is when it happens) the italicized text changes to the type “Book Antiqua Italic”, but remains set in italics, the “I”-button is active, It is consequently doubly italicized. (Not very nice to look at, and hard to read. It leans a lot.) One time it became bold as well (even less nice to look at…). A bug?
I use Dejavu Serif, and it comes with a Bold, an Italic, a Book, and a Bold Italic version. Those are what’s listed in the font style selector (Book, Italic, Bold, Bold Italic). Fonts with Semibold versions should have that listed in the font selector. Technically speaking, italicizing a font without the font’s “italic” version is “oblique,” not “italic.” And applying obliqueness to an italic font… well…
I’d call it a bug, myself.
Thanks! Makes total sense that they have the button “I” for it then 
I had to look up the difference between oblique and italic, and yes, the thing that happpens when I press “I” is actually italics (which is probably not the case for all fonts). The letters are not only slanted, but are changed - “a” loses its “roof” for instance. It looks just as Book antiqua italic. But when this problem occurs, Book antiqua italic is even more slanted, almost lying down…
I noticed a bit more about this problem, and I think it verges om some other bugs people have been reporting, but I explain it anyway.
I use Book Antiqua. When I cut and paste text in italics (created by ctrl+I), it transforms to Book Antiqua Italics, stlll set in Italics, so it slants way too much. Often it is also set in bold.
The same happens when a text is synched with external folder.
To set it right, I use “Convert text to default formatting”. It is easier to just remove the Ctrl+I and have Book Antiqua Italics. It looks right, but the italics then gets lost in compile.
I don’t know if you have tried to fix this, I still get this problem. Text set in italics by ctrl+I transforms to the font Book Antiqua italic, and remains in italics, when syncing with external folder (I think that is when it happens), so it “leans” a lot.
The workaround is to “Convert text to default formatting”, but I have to do this once and again.
I don’t use styles.