If you make something smallcaps and then zoom, the smallcaps letters won’t scale with the rest of the text.
I think this is a Qt bug. I maintain a Qt project that uses a QTextEdit and I notice the problem there too with QFont::setPointSize.
Thanks for the report! That is easy enough to reproduce; I’ve got it written up.
Okay, yes, to confirm this is a Qt bug they have known about for a long time, and it has been filed with—well I was going to say Trolltech; showing my age a bit there. 
Thanks. Do you have a link to the bug or know if they’re planning on fixing it any time soon?
I don’t know anything about that, sorry.