Make Hover Content Dismissible, Hoverable and Persistent
MUST: Hover/focus popups must be DISMISSIBLE (Escape hides it without moving pointer or focus), HOVERABLE (the pointer can travel into the content and stay there — bridge the trigger/card gap with wrapper padding, not a margin) and PERSISTENT (no auto-hide timer; it stays until the trigger is left, the user dismisses it, or the info goes stale). WCAG SC 1.4.13 Content on Hover or Focus, Level AA.
Let Escape close a hover card, let the pointer enter it, and never expire it on a timer
Bad
Good
Why it matters
The missing sibling of the two tooltip rules already here. "Tooltip Timing" governs the show-delay; "No Interactive Content in Tooltips" governs what may go inside. Neither says what happens once the thing is on screen — and that is where three separate, independently-failing requirements live. DISMISSIBLE: Escape must hide it without moving the pointer or focus, because a screen-magnifier user viewing a small slice of the page may have a popup covering the content they were reading, and forcing them to move the pointer costs them their place.
HOVERABLE: the pointer must be able to travel into the content and stay there, which is why the classic 2px "breathing gap" between trigger and card is a bug, not a detail — crossing it fires mouseleave and the card evaporates. Bridge it with padding on the wrapper (an invisible safe area) rather than a margin on the card, or hit-test a safe triangle toward the card.
PERSISTENT: no auto-hide timers. A 3-second dismissal is an eternity for a magnifier user panning across the card and no time at all for someone reading with a screen reader; the content stays until the trigger is left, the user dismisses it, or the information stops being true.