a few moments ago, I realized that all the text formatting (italic, underline etc.) that I had applied to my customized output style was suddenly gone in my document after refreshing the citations.
It is also not possible anymore in the EndNote style editor to just re-apply them: When I mark a word (like “Author”) and hit cmd-I (for italic), nothing happens. This was the way I previously formatted the components, though.
In the DIsplay Fonts panel of the (general) preferences, I had the font set to a font that doesn’t feature an italic typeset (Lucida Sans Unicode), so this font was used in the Edit Output Style panel as well. Apparently the style was left untouched until I opened the Edit Output Style panel again, and the changes were erroneously applied by EndNote only upon opening the editor.
Changing it IN THE PANEL (using cmd-T to open the Text Formatting palette, mark the text in the Templates panel, change font) does the trick. Hope this helps someone with the same problem in the future.
@EndNote Support: Maybe you want to forward this to development; it’s not a real bug, but it’s very confusing anyway. Thanks!