Is it possible to block a contact without first signing in to the skype client? How
Not only can you not manage your contacts offline, but it appears (after some googling) there's no supported way of logging in as offline, unless you logged off last time as offline.
I imagine you want to be able to block someone without appearing as online first, even for a moment.
I found this link... but I'm not desperate enough to try it - I certainly do not recommend it without careful checks for malware first.