This is a version construction, where the prefix before the plus sign is
taken from the version of a binary package, and the suffix is derived
from another source package (i.e. a source package building using the
source packaged as a binary).

$ dpkg --compare-versions 2.47-2+1 lt 2.47-2ubuntu1+1; echo $?
1

Apparently, the -2 and -2ubuntu1 should be parsed as belonging to the
prefix.  Is this a known thing, and working as designed, or is this
something that should/could be fixed?

tag 1146868 wontfix
thanks

Hi!

This is how the algorithm has worked for a very very long time (as
documented in deb-version(7) and Debian Policy), I don't see anything
to fix here. Also even if we wanted, that would break so much stuff,
and would need coordination with so many implementations, that I don't
think it would be feasible anyway). Thus closing.

Thanks,
Guillem