Fix so hints are positioned in front of positioned elements with z-index as they fade in/out, and so the matched hint is positioned in front of other hints.
Fix how events are stopped when Key Jump catches an event. And catch all keydown events when Key Jump is active.
Run the contentscript at document_start instead so it registers its event handler before any from the page so it can stop any page event when needed.
Do not add a character to the hint query if it would result in no match.