I promised I'd tell you when things got cleared, and they did. I spoke to C2Media who I helped finding out a bug that has been there for some people. This bug made the sponsor program "resist" the uninstallation, and keep working.
Luckily, I'm happy to tell everyone that not only my problem got solved, but probably the same problem won't occur anymore in future versions of the sponsor uninstaller that's integrated in Messenger Plus! (triggered when Messenger Plus! gets uninstalled)
So there won't be more paranormal stories about people not being able to remove C2Media adware.
See you in Paris
(huh maybe
)