This is a limitation of Windows 8/10. Microsoft has decided not to update the way MDI windows are displayed in newer versions of Windows because MDI window support has been deprecated. They want all applications to become SDI (to display only one window at a time) which would essentially be like keeping windows maximized all the time. However, MDI windows are useful in IRC as they allow you to watch multiple contexts at a time, so this is not a feature I plan to remove.