The P5 content model for <dateline> follows P4 in
limiting permitted content to text plus a handful of
tags: date, time, name, address. This is way too
confining. Datelines commonly contain styled text
(needing a <hi> tag), and often need <ref> or <ptr>,
for example in a print edition where a note is attached
internally in a dateline.
Is there any reason not to give <dateline> the same
content model as <salute>? So far as I can see that
would be a superset of the existing content model and
therefore should be backwardly compatible with P4. No?