During a transition, like fading-in/ fading-out panels, interaction with the contents of the UI elements that is subject of the transition is pointless and yields a jarring user experience. It is best, in general, to disable direct interaction with an element during its transition phase. I practice this would mean to disallow mouse-pointer events during the time a (CSS) transition takes. This bug serves as a meta/ tracking bug to track all areas where this improvement can be applied.