The correct thing to do would be to put different unrelated APIs into their own library, instead of everything into libsystemd0. This has always been one of my biggest issues with it. It makes it hard to replace just one API from that library, because on a binary distribution, only one package can provide it. And as a nice side effect, surprises like this one could then be avoided.
systemd developers have already rejected that approach, so I guess we will end up with lots of reimplementations, both in individual projects and third-party libsystemd-notify style libraries.
I see that different clients implemented in different languages will need different client-libraries and maintaining all that is not something, a core project is going to do but if using the raw protocol instead of the convenience of libsystemd is a (commonly ignored) recommendation which makes a lot of sense in terms of segmentation, providing at least one reference implementation would point all systemd users into the right direction.
Recommending that each client should just implement the (trivial) protocol access itself does not make so much sense to me.
