The most annoying thing about Windows Store apps is that no text, apart from what is rendered inside an editable control, is selectable (and copiable).
Right-click on any file in Explorer, and you can still highlight and copy the property values of the given file even though the text is readonly.
Granted, the use cases for the copiability of the file property values are limited, but consider what you're unable to do when you're, say, looking at the description of an app listed in the Windows Store using the Windows Store app. Go to any title, and then try to select and copy the description of the app. You're unable to.
Let's say you wanted to report the app to Microsoft or contact the author and needed to reference the description. You'd have to manually type it. This is one the main reasons why I can't stand using any Windows Store apps other than games.
Ha, this has been my major annoyance as well. I'm glad I'm not alone.