[GhostVII]

That's really not a hard problem to solve though, as an application developer you can just have a default theme for your app, and have some checkbox somewhere letting the user use their OS theme instead of the app default.

Or you can just accept that whenever you let someone configure the UI in an advanced way, it is possible for them to make the UI more confusing. Just because it is possible for someone to mess up your app with a bad config, doesn't mean it is best to remove any kind of configuration at all.