:abbr: markup is not obvious in some browsers (like Safari)
Reviewing the draft Python devguide, it was noted that usages of :abbr:, resulting in <abbr>, were not noticeable at all in Safari unless the user happened to mouse over. It was reported that Chrome gives no visible clues as well, unlike Firefox. If there is nothing that can be done in Sphinx (via CSS attributes?), perhaps the documentation should warn about it.