The selection end seems to be fixed to the bottom of the page.
Marked as blocking GCLI-HELP because it's really annoying, but I've not checked if this affects the FF integration.
// Commenting this out is a quick workaround for bug 653140 but it probably
// breaks the popup mechanism, however for now selection is more important
// that popup.
// this.element.addEventListener('mousedown', this.preventBlur, true);
See changeset c80dc66
Moving to block GCLI-FUTURE because we have a workaround