Sebastien, according to the NotifyOSD wiki merging requires the "x-canonical-append" hint. I'm not sure, but this looks like something specific to Ubuntu.
https://wiki.ubuntu.com/NotifyOSD#Treatment%20of%20the%20Desktop%20Notifications%20Specification%201.1 -- Notifications do not merge when coming from the same contact https://bugs.launchpad.net/bugs/408294 You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to empathy in ubuntu. -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
