For keyref processing in general, we have decided that the content of
the keyref-bearing element should always be displayed if it exists.
However, for <abbreviated-form> processing I'm starting to think that
local content should lose if the key can be resolved to a
<glossAcronym>. If we have local content always win, the only way to
have the feature work will be to leave the <abbreviated-form> element
empty. But to be safe, practitioners should put something reasonable in
<abbreviated-form> so that there is fallback text if the keyref can't be
resolved or if the processor is not sophisticated enough to do the
special processing required to render abbreviations.