"Navigation popups" has problems with this also, but in its own way. When hovering over the ref label (in the %2E case, at least), it does give a popup, but the popup does not contain the normal contents it is supposed to deliver, namely the text displayed in the reference note. (Instead it just shows the plain popup for the page, which is the text of the intro.) You can see this by hovering over the %2E example label [8], contrasted with hovering over [7], which does not have problem characters.