Given that Rosetta doesn't support the Gettext domain declaration, I wouldn't encourage Plone to start using that.
It would be marginally nicer if the "Domain" header were an "X-Domain" header, but it's not of any practical difference as far as I can tell.
If all PO templates had a Domain header, it would make things a lot easier for Rosetta -- we could make most of Martin's hacks for working out the domain go away, I think.
Given that Rosetta doesn't support the Gettext domain declaration, I wouldn't encourage Plone to start using that.
It would be marginally nicer if the "Domain" header were an "X-Domain" header, but it's not of any practical difference as far as I can tell.
If all PO templates had a Domain header, it would make things a lot easier for Rosetta -- we could make most of Martin's hacks for working out the domain go away, I think.